Added built-in script language

Added a bunch of features - plates calculator (like, what plates I should add to a barbell to get necessary weight), cloud storage, progress graphs.

Having to edit code and redeploy the app to make changes in the program sucks. How could I make it more convenient?

After thinking about it a lot, I decided to make a built-in scripting language, which I could use to describe the logic of the workouts and logic of progressions/deloads. Never wrote programming languages before, needed to learn that first :)

Finally, I did that. Called it Liftoscript, it now allows to express any logic of workouts based on completed reps, completed weights, various state variables you can create. That was a huge feature to lift!