refactor(configs): move defaults to 'configs'

[linrongbin16]

Regression Test

Platforms

• [ ] windows
• [x] macOS
• [ ] linux

Hosts

• [x] Test on github.com.
• [ ] Test on gitlab.com.
• [ ] Test on bitbucket.org.
• [ ] Test on codeberg.org.
• [ ] Test on git.samba.org.

Functions

• [x] Use GitLink to copy git link.
• [x] Use GitLink! to open git link in browser.
• [x] Use GitLink blame to copy the /blame git link.
• [x] 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[bot]]

Codecov Report

Attention: Patch coverage is 87.13450% with 22 lines in your changes are missing coverage. Please review.

Project coverage is 74.11%. Comparing base (cc3e1b2) to head (7771619).

:exclamation: Current head 7771619 differs from pull request most recent head a228d0d. Consider uploading reports for the commit a228d0d to get more accurate results

Files	Patch %	Lines
lua/gitlinker/configs.lua	88.00%	18 Missing :warning:
lua/gitlinker.lua	80.95%	4 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #210 +/- ## ========================================== + Coverage 73.45% 74.11% +0.66% ========================================== Files 8 9 +1 Lines 727 734 +7 ========================================== + Hits 534 544 +10 + Misses 193 190 -3 ```

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