Add highlight groups for TS diff

[evantravers]

I searched around and found the groups in other themes.

Fixes #100.

References:

• https://github.com/EdenEast/nightfox.nvim/commit/a201f5fc008fc1c12d68f1dbe855d3f29bb2a4c9
• https://github.com/bluz71/vim-moonfly-colors/commit/b194851ad2f096741d674a426ef510c8901d71a6

[evantravers]

Looks like it works!