Fix missing full stop (`.`) in the CONTRIBUTING.md

[johlju]

Pull Request

Pull Request (PR) description

Fixed

• Fixed missing full stop (.) in the CONTRIBUTING.md. Fixes #333.

Fixes #333

Task list

• [x] The PR represents a single logical change. i.e. Cosmetic updates should go in different PRs.
• [x] Added an entry under the Unreleased section of in the CHANGELOG.md as per format.
• [x] Local clean build passes without issue or fail tests (build.ps1 -ResolveDependency).
• [ ] Documentation added/updated in README.md.
• [ ] Comment-based help added/updated.
• [ ] Localization strings added/updated in all localization files as appropriate.
• [ ] Unit tests added/updated. See DSC Community Testing Guidelines.
• [ ] Integration tests added/updated (where possible). See DSC Community Testing Guidelines.
• [ ] New/changed code adheres to DSC Community Style Guidelines.

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This change is 

[codecov[bot]]

Codecov Report

Merging #343 (d8bd733) into main (3432474) will not change coverage. The diff coverage is n/a.

@@         Coverage Diff         @@
##           main   #343   +/-   ##
===================================
  Coverage    28%    28%           
===================================
  Files        40     40           
  Lines      2164   2164           
===================================
  Hits        608    608           
  Misses     1556   1556