feat(battery): add Mastodon tips

[seberm]

Describe the changes you have made in this PR

Add tipping for Mastodon instances.

Link this PR to an issue [optional]

• https://github.com/getAlby/lightning-browser-extension/wiki/Bounties#add-tipping-support-for-mastodon-instances
• Tipping feature for Mastodon instances #476
• feat: tipping support for mastodon #826

Type of change

• feat: New feature (non-breaking change which adds functionality)

How has this been tested?

Currently only on libretooth.gr. It's still WIP.

Checklist

• My code follows the style guidelines of this project and performed a self-review of my own code
• New and existing tests pass locally with my changes
• I checked if I need to make corresponding changes to the documentation (and made those changes if needed)

[seberm]

Oh, I've found there is already an existing PR for Mastodon support (#826). I've misread the Bounty page and missed the issue link :/ (#476).

So I suppose we will close this one and we continue the work in #826.