add control for user to scale the size of results cards

[micahstubbs]

may provide better accessibility and a better experience on some screen sizes. might be nicer than
just cmd + browser zoom

for accessibility and scannability purposes i'd bump up the font sizes for 'block-description' to 18/24 and 'block user' to 14/18

taking this advice, working back to the problem statement, and imagining a different solution. increasing the size of the block description and the block user text without increasing the size of the block result card doesn't look quite right 🤔

inspired by #12