feat(theme): add RTLService service

[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

[codecov]

Codecov Report

Merging #1120 (5317456) into master (9ea783e) will decrease coverage by 0.08%.
The diff coverage is 84.61%.

@@            Coverage Diff             @@
##           master    #1120      +/-   ##
==========================================
- Coverage   96.19%   96.11%   -0.09%     
==========================================
  Files         237      238       +1     
  Lines        7496     7547      +51     
  Branches     1359     1363       +4     
==========================================
+ Hits         7211     7254      +43     
- Misses        149      153       +4     
- Partials      136      140       +4     

Impacted Files	Coverage Δ
packages/theme/src/services/rtl/rtl.service.ts	84.00% <84.00%> (ø)
packages/abc/avatar-list/avatar-list.component.ts	94.87% <100.00%> (+0.13%)	⬆️

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[ng-alain-bot]

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