feat(rules): add 'override_rules' to override default 'pattern_rules'

[linrongbin16]

Regression Test

Platforms

• windows
• macOS
• linux

Tasks

• Use <leader>gl to copy git link.
• Use <leader>gL to open git link in browser.
• Copy git link in a symlink directory of git repo.
• Copy git link in an un-pushed git branch, and receive an expected error.
• Copy git link in a pushed git branch but edited file, and receive a warning says the git link could be wrong.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Files	Coverage Δ
lua/gitlinker.lua	63.70% <100.00%> (-8.06%)	⬇️

... and 4 files with indirect coverage changes

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