Website: support GH page links to canonical src

[chalin]

Closes open-telemetry/opentelemetry.io#542

/cc @austinlparker

[codecov]

Codecov Report

Merging #454 (68545d6) into main (f5f57f7) will not change coverage.
The diff coverage is n/a.

❗ Current head 68545d6 differs from pull request most recent head ddbdf49. Consider uploading reports for the commit ddbdf49 to get more accurate results

@@            Coverage Diff            @@
##               main     #454   +/-   ##
=========================================
  Coverage     91.19%   91.19%           
  Complexity      809      809           
=========================================
  Files            76       76           
  Lines          1988     1988           
=========================================
  Hits           1813     1813           
  Misses          175      175           

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