Add Fastlane metadata

[MajoranaOedipus]

Fastlane metadata added, c.f. https://gitlab.com/-/snippets/1895688

So that we can prepare for the release to F-Droid (#115).

The descriptions are taken from the website https://commet.chat/,
and I just randomly take three screen shots featuring Space and Room chat (in day and night mode).

This PR is a draft. If @Airyzz think this is fine, I would continue to add the corresponding Chinese and Japanese languages (I only speak these two plus English). So we need volunteers to add more languages.

[Airyzz]

Thank you, i made a few tweaks to the text and replaced the images - would love for you to help with translations if you want to!

[MajoranaOedipus]

Hi, I translated the metadata to Chinese and Japanese.

Would you like to re-tag this as v0.3.1+hotfix.1 (or a -fdroid postfix, the F-Droid server can use commit tags to check updates)?

[Airyzz]

thank you for translating! I'm planning to release v0.4 very soon, and since the metadata and images in this PR are based on latest build, it would be a bit misleading to have this metadata for 0.3.1, so i suggest waiting until the next release for F-Droid?

also, is a tag with -fdroid required for their server to check updates? or can it be any tag?

[MajoranaOedipus]

Sure, looking forward to the release! Very cool app.

-fdroid is not required, so you can just tag like you have been doing before.