Extract classes for tailwind css

[RomainClem]

Right now there's a lot of copy everywhere for css, which actually makes it a bit difficult.

It would be interesting to follow this feature from tailwind css and create "Base" class that can be copied around.

https://tailwindcss.com/docs/reusing-styles#extracting-classes-with-apply

[RomainClem]

Exercise creation modal

• [x] HR
• [ ] button
• [ ] input