Add browse filters to api doc, filter by friendly game version

[HebaruSan]

This is tying up some loose ends from #466.

• The game_version filter is renamed game_version_id to indicate that it accepts a game database id, not a friendly string
• A new game_version filter is added that does accept a friendly string (like "1.12.5")
• The API documentation is updated to reflect the changes from both PRs

[HebaruSan]

Looks good after b274d208db098e252766fc0f084de04d0422bc59 :

• https://alpha.spacedock.info/api/1/versions
• https://alpha.spacedock.info/api/browse?game_id=1&game_version=1.0
• https://alpha.spacedock.info/api/browse?game_id=1&game_version=1.12.3
• https://alpha.spacedock.info/api/browse?game_version_id=1