docs: increase contrast in home CTA and search

[nedjulius]

Addresses the issue #76

Changed contrast color for both CTA and search placeholder texts.

Before	After

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[nmn]

I think this PR goes a bit too far.

1. To improve the contrast of the CTA, I'll tweak the shade of pink being used instead.
2. The search placeholder now no longer looks like a Placeholder.

Could you revert the CTA change, and choose a medium color for the placeholder?

[nedjulius]

@nmn reverted CTA changes, changed the placeholder color to a dimmer one