(GH-2) Fix menu icons for dark theme

[agc93]

Applies the same fix to the "Cake Build" menu icons as the template icons to prevent inverted colors on dark themes.

Resolves #2 (again)

[gep13]

Rebased and merged here: https://github.com/cake-build/cake-vs/commit/7bd1714658afd35492567a12e07571530b7478c2