FEAT: Add option to use num of core for doc build

[dipinknair]

Tested in embedding examples repo https://github.com/ansys/pymechanical-embedding-examples/actions/runs/16144271451/job/45558949601?pr=266

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
✅ +0.02% (target: -1.00%)	✅ 100.00%

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (4b0d10c)	2537	2193	86.44%
Head commit (4c24e74)	2541 (+4)	2197 (+4)	86.46% (+0.02%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#1230)	4	4	100.00%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.46%. Comparing base (4b0d10c) to head (4c24e74).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1230      +/-   ##
==========================================
+ Coverage   86.44%   86.46%   +0.02%     
==========================================
  Files          39       39              
  Lines        2537     2541       +4     
==========================================
+ Hits         2193     2197       +4     
  Misses        344      344              

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