Fix VSCE artifact build due to restricted SVG image policy
Fix VSCE artifact build due to restricted SVG image policy

Due to the restricted security policy of the `vsce` packaging and
publishing tool (1) the SVG images used in the `CHANGELOG.md` have
been removed in order to fix the build process.

References:
  (1) https://code.visualstudio.com/api/working-with-extensions/publishing-extension#publishing-extensions

Fixes GH-137

arcticicestudio/nord-visual-studio-code,arcticicestudio/nord-visual-studio-code