custom.js configurable linkbutton

[darkelement1987]

My first coding project, still learning. Be nice please :p i wanna thank @Qualimiox for inspiring me to do this PR.

Description

Set values in custom.js to configure/show button

    // customLink Button Settings
    const customLinkButtonEnabled = true // Default: False. 
    const customLinkTitle = 'Test' // Default: ''
    const customLinkUrl = 'http://test.nl' // Default: ''

Todo/Doesn't work yet

• [x] Make the button show even if people decided to remove stats/status/whatever button

document.getelementbytag / appendchild stuff?

Done

• [x] Title/URL configurable in custom.js
• [x] Enable/disable in custom.js
• [x] Make the scss-file grab the right url from custom.js (no idea how)
• [x] Make the link use css + fontawesome

Motivation and Context

How Has This Been Tested?

Locally with lots of frustration

Screenshots (if appropriate):

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)~~

Checklist:

• [x] My code follows the code style of this project.~~
• [ ] My change requires a change to the documentation.~~
• [ ] I have updated the documentation accordingly.~~

[darkelement1987]

Review again please.

[darkelement1987]

Changes made + tested, works now. Need review+test

[darkelement1987]

Just tested this some more. On /stats /status pages this stuff will error @ browser console:

jquery.min.js:2 jQuery.Deferred exception: Cannot read property 'insertAdjacentHTML' of null TypeError: Cannot read property 'insertAdjacentHTML' of null
    at HTMLDocument.<anonymous> (https://map.tjielup.nl/static/1d458ea/dist/js/custom.min.js:5:7682)
    at j (https://cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js:2:29999)
    at k (https://cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js:2:30313) undefined

Which makes sense because there is no 'stats' button there :eyes: maybe this stuff should be added in config.ini/map.html instead?