feat(url): support url template

[linrongbin16]

Regression Test

Platforms

• windows
• macOS
• linux

Tasks

• Use GitLink to copy git link.
• Use GitLink! to open git link in browser.
• Use GitLink blame to copy the /blame git link.
• Use GitLink! blame to open the /blame 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

Attention: 21 lines in your changes are missing coverage. Please review.

Comparison is base (a705085) 75.87% compared to head (fb3803f) 76.71%.

Files	Patch %	Lines
lua/gitlinker.lua	84.61%	20 Missing ⚠️
lua/gitlinker/range.lua	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #128      +/-   ##
==========================================
+ Coverage   75.87%   76.71%   +0.84%     
==========================================
  Files          11       11              
  Lines         800      902     +102     
==========================================
+ Hits          607      692      +85     
- Misses        193      210      +17     

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