OpenTyrian2000: game data and persistence

[mundifex]

Changes:

• persist config files and save data
• automatically download freeware game data files
• remove notes field

Closes #1185

• [x] I have read the Contributing Guide.

[github-actions[bot]]

All changes look good.

Wait for review from human collaborators.

opentyrian2000

• [x] Description
• [x] License
• [x] Hashes
• [x] Checkver
• [x] Autoupdate

[mundifex]

Closes #1185