v3.5.2: Chore

Bugfixes

• [Fixed] Guild only (slash) commands is registered to DMs
• [Fixed] Duration parser stopped working
• [Fixed] 1 spam is parsed as 1 seconds
• [Fixed] >mute set command stopped working

Improvements

• [Changed] Rename some command (only affecting for slash)
• [Improved] Use SQLite by default when DB_URL is not specified

Internal Changes

• [Changed] Turn monkeypatches into wrapper classes to clean up the
  codebase
• [Improved] Add __init__.py file to clean up the codebase
• [Fixed] Updated discord.py to v2.1.1 to fix GIF sticker support
• [Fixed] Added missing license headers