issue search: support github search query syntax

[milahu]

Feature Description

github search query syntax - example queries:

• (in:title output)
• (in:body "Thanks for reporting")
• (in:title default) AND (in:body openshift)
• (in:title default) OR (in:title labels)
• type:issue is:open
• is:pr state:closed
• author:lunny

docs:

• Searching issues and pull requests
• Filtering and searching issues and pull requests

keywords:

• GitHub search query syntax
• GitHub search qualifiers
• GitHub search operators
• GitHub advanced search syntax
• GitHub issue search qualifiers
• boolean operators
• search filters

related

• [Feature Request] Add detailed search #14779 - test in:file stars:>100
• feat: commenter/commented search filter for issues/PRs forgejo#7827 - commenter:@me
• Advance search gitea for global issues - assignee:username

Screenshots

No response