Docsy theme adjustments

[ajschmidt8]

As part of https://github.com/rapidsai/rapids.ai/issues/334, I migrated rapids.ai to Docsy.

However, there are still some adjustments that need to be made.

Specifically, the following changes:

• [x] Move the fs, m{t,b}, p{t,b} styles in https://github.com/rapidsai/rapids.ai/pull/341 to the Bootstrap configuration
• [ ] On mobile, move the hamburger menu to the top left and logo to the top right to match PyData Sphinx theme
• [x] Implement local search (explore Algolia as a future enhancement)