Make match_path OS agnostic

[mvelikikh]

page.file.src_path on Windows contains backslashes resulting in an empty RSS feed if match_path contains a forward slash. This commit replaces src_path with src_uri which provides an OS independent path with forward slashes '/'.

fixes #321

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.70%. Comparing base (a168516) to head (020d441).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #323   +/-   ##
=======================================
  Coverage   80.70%   80.70%           
=======================================
  Files          10       10           
  Lines         653      653           
  Branches      134      134           
=======================================
  Hits          527      527           
  Misses         86       86           
  Partials       40       40           

Flag	Coverage Δ
unittests	80.55% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
mkdocs_rss_plugin/plugin.py	90.51% <100.00%> (ø)

[Guts]

Thanks @mvelikikh and welcome to the contributors :).