feat(theme): add provideAlain

[cipchk]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/ng-alain/delon/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Application (the showcase website) / infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[ ] No

Other information

[ng-alain-bot]

Preview is ready!

[codecov]

Codecov Report

Merging #1697 (c630059) into master (683ab23) will decrease coverage by 0.07%.
The diff coverage is 25.00%.

❗ Current head c630059 differs from pull request most recent head 51d91d8. Consider uploading reports for the commit 51d91d8 to get more accurate results

@@            Coverage Diff             @@
##           master    #1697      +/-   ##
==========================================
- Coverage   95.52%   95.46%   -0.07%     
==========================================
  Files         299      300       +1     
  Lines        8828     8836       +8     
  Branches     1660     1660              
==========================================
+ Hits         8433     8435       +2     
- Misses        325      331       +6     
  Partials       70       70              

Files	Coverage Δ
...es/theme/src/services/settings/settings.service.ts	96.42% <100.00%> (+0.06%)	⬆️
packages/theme/src/provide.ts	0.00% <0.00%> (ø)
packages/theme/src/theme.module.ts	60.00% <20.00%> (-40.00%)	⬇️