fix: rely on data.locale for permalink generation

[greatislander]

eleventy-plugin-i18n-gettext sets two variables based on the locale directory within the enhance11tydata() method:

• locale: language and country code, e.g. en-CA
• lang: language code, e.g. en

This PR fixes an issue where a locale could not be matched because the search string was the short lang value (en) but the set of locales being searched was indexed using the full locale (en-CA`) value.

[codecov]

Codecov Report

Merging #198 (781dce7) into main (226dc6f) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #198   +/-   ##
=======================================
  Coverage   97.05%   97.05%           
=======================================
  Files          14       14           
  Lines         679      679           
=======================================
  Hits          659      659           
  Misses         20       20           

Files Changed	Coverage Δ
src/utils/generate-permalink.js	100.00% <100.00%> (ø)