Add GitHub contribution templates

[austin-smith]

What Changed

• Added BitDream-aligned bug report and feature request forms.
• Added the same concise pull request template used by BitDream.
• Added BitDream-aligned branch, commit, pull request, and issue conventions to AGENTS.md.

Why

Use the established BitDream contribution workflow consistently in webhooks.lol without adding extra project-specific fields or policy.

Validation

• Parsed every issue-template YAML file successfully.
• Confirmed the feature request form, blank-issue config, and pull request template match BitDream exactly.
• Ran git diff --cached --check successfully before each commit.
• No application tests were run because these changes only affect repository documentation and GitHub templates.