[v3] Add `port` flag to dev command

[abichinger]

Description

This PR adds the following flag to the dev command:

• vport: The vite dev server port, default: 9245

And adds support for the environment variable WAILS_VITE_PORT

server.strictport is set to exit if the specified port is already in use.

Fixes #3379

Type of change

• [x] New feature (non-breaking change which adds functionality)

How Has This Been Tested?

The following commands have been executed inside a new project:

wails3 dev                                   # Port: 9245
wails3 dev -port 3333                        # Port: 3333
WAILS_VITE_PORT=3333 wails3 dev             # Port: 3333
wails3 task dev                              # Port: 9245
wails3 task dev VITE_PORT=3333               # Port: 3333
WAILS_VITE_PORT=3333 wails3 task dev        # Port: 3333
WAILS_VITE_PORT=3333 wails3 dev -port=2222  # Port: 2222

Executing wails3 dev twice triggered the following error message:

  ERROR   listen tcp 127.0.0.1:9245: bind: address already in use

• [ ] Windows
• [ ] macOS
• [x] Linux

Test Configuration

# System
┌───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
| Name         | Manjaro Linux                                                                                                  |
| Version      | Unknown                                                                                                        |
| ID           | manjaro                                                                                                        |
| Branding     |                                                                                                                |
| Platform     | linux                                                                                                          |
| Architecture | amd64                                                                                                          |
| CPU          | AMD Ryzen 5 3600 6-Core Processor                                                                              |
| GPU 1        | Navi 10 [Radeon RX 5600 OEM/5600 XT / 5700/5700 XT] (Advanced Micro Devices, Inc. [AMD/ATI]) - Driver: amdgpu  |
| Memory       | 32GB                                                                                                           |
└───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

# Build Environment
┌─────────────────────────────────────────────────────────────────────────────────────────────────┐
| Wails CLI      | v3.0.0-alpha.4                                                                 |
| Go Version     | go1.22.0                                                                       |
| Revision       | 1b288a0a1a37c849a4edc22430b372e8469308ec                                       |
| Modified       | true                                                                           |
| -buildmode     | exe                                                                            |
| -compiler      | gc                                                                             |
| CGO_CFLAGS     |                                                                                |
| CGO_CPPFLAGS   |                                                                                |
| CGO_CXXFLAGS   |                                                                                |
| CGO_ENABLED    | 1                                                                              |
| CGO_LDFLAGS    |                                                                                |
| DefaultGODEBUG | httplaxcontentlength=1,httpmuxgo121=1,tls10server=1,tlsrsakex=1,tlsunsafeekm=1 |
| GOAMD64        | v1                                                                             |
| GOARCH         | amd64                                                                          |
| GOOS           | linux                                                                          |
| vcs            | git                                                                            |
| vcs.modified   | true                                                                           |
| vcs.revision   | 1b288a0a1a37c849a4edc22430b372e8469308ec                                       |
| vcs.time       | 2024-04-23T14:32:21Z                                                           |
└─────────────────────────────────────────────────────────────────────────────────────────────────┘

# Dependencies
┌───────────────────────────┐
| gcc        | 13.2.1-5     |
| libgtk-3   | 1:3.24.41-1  |
| libwebkit  | 2.42.5-2     |
| npm        | 10.5.0       |
| pkg-config | 2.1.0-2      |
└─ * - Optional Dependency ─┘

# Diagnosis
 SUCCESS  Your system is ready for Wails development!

Checklist:

• [x] I have updated website/src/pages/changelog.mdx with details of this PR
• [x] My code follows the general coding style of this project
• [x] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally with my changes