Syntax highlighting

[daun]

Description

• Allow syntax highlighting in diff views
• Allow copying diff blocks without selecting the +/-
• Enable light theme in code blocks when in light mode
• Pretty messy implementation, had to clone and fix a node lib that wouldn't compile
• Need to clean up the lib and merge updates upstream in a second step

Before

After

Light mode

Checks

• [x] The PR is submitted to the next branch
• [x] The code was linted before pushing (npm run lint)
• [x] All tests are passing (npm run test)
• [ ] New or updated tests are included
• [ ] The documentation was updated as required