feat(service): add lark service

[immanuelhume]

Description

Adds a notifier service for Lark.

Motivation and Context

This addresses https://github.com/nikoksr/notify/issues/268.

Lark has three kinds of bots, referred to as "webhook", "custom app", and "store app" bots. The first two are supported through this PR, which explains the two different files webhook.go and custom_app.go. The store apps have a tricky API which would work against the simple style of this library so they are not included here.

How Has This Been Tested?

Basic unit tests using mocks have been written. Manual testing has also been performed.

Screenshots / Output (if appropriate):

The first screenshot is with a webhook. The second is with a custom app.

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Documentation (no code change)
• [ ] Refactor (refactoring production code)
• [ ] Other

Checklist:

• [x] My code follows the code style of this project.
• [x] I have updated the documentation accordingly.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.

[nikoksr]

@immanuelhume so sorry for the very late response.

I fixed the compatibility issues with the main branch and some linter warnings. Please check those before you push next time, please.

I greatly appreciate your patience and contribution!

[immanuelhume]

@nikoksr Sorry I must've missed those warnings. Thanks for maintaining this project!