fix: allow dash as tag name in markdig code snippet syntax

[yufeih]

fixes #8777

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.02 ⚠️

Comparison is base (185afe1) 76.96% compared to head (7261396) 76.94%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8783      +/-   ##
==========================================
- Coverage   76.96%   76.94%   -0.02%     
==========================================
  Files         606      606              
  Lines       25054    25054              
==========================================
- Hits        19282    19279       -3     
- Misses       5772     5775       +3     

Impacted Files	Coverage Δ
...ine.Extensions/CodeSnippet/CodeSnippetExtractor.cs	100.00% <100.00%> (ø)

... and 2 files with indirect coverage changes

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