create high contrast mode

[julesparra]

@AkiPraveen, info below was our original outline for HCM, but feel free to implement your plan.

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requirements:

1. alternative stylesheet for each page (home, sponsor, and donate) that override original styling
2. button on each page to toggle high contrast mode on/off

changes needed in alternative stylesheet:

• use ms-high-contrast CSS media feature to detect Microsoft High Contrast Mode & what version: https://developer.mozilla.org/en-US/docs/Web/CSS/@media/-ms-high-contrast
• make background colors white & update white text to black & colored text to brighter color (e.g. lavender -> neon purple)
• use black borders to define buttons/other elements

👀 Bootstrap switch - fill should be pink & default state should be "off" (add to leftmost part of navbar, decrease side space between navbar links)

you can test on Windows with High Contrast Mode (try all options)!

🆘 reference with comparative examples