Fix CODEOWNERS: correct @jeschulz -> @jesperschulz on base rules

[JesperSchulz]

Problem

GitHub's CODEOWNERS validator (gh api repos/microsoft/BCQuality/codeowners/errors) flagged the handle @jeschulz as an Unknown owner. This is a typo — the repo owner's correct, valid handle is @jesperschulz, which is already used and accepted on the style line (/microsoft/knowledge/style/).

As a result of the typo, the base rules /microsoft/, /skills/, and /.github/ had no valid code owner.

Change

Replaced @jeschulz with @jesperschulz on the three base-rule lines only:

• /microsoft/ @jeschulz → /microsoft/ @jesperschulz
• /skills/ @jeschulz → /skills/ @jesperschulz
• /.github/ @jeschulz → /.github/ @jesperschulz

After the change there are 0 occurrences of @jeschulz and 4 of @jesperschulz. No other lines were touched.

Notes

• The domain-expert reviewer lines were left untouched.
• The domain-expert reviewers still require write access to the repo to be auto-requested; that is handled separately by the owner.

Validation

• python .github/scripts/validate_frontmatter.py --root . → 0 errors / 0 warnings
• pwsh .github/scripts/Test-KnowledgeIndex.ps1 -Root . → PASSED, 191 articles

Co-authored-by: Copilot 223556219+Copilot@users.noreply.github.com