Explain concepts and acronyms we use in the Roc repo wiki

[Anton-4]

We regularly use acronyms and there are plenty of complicated concepts in compilers. It would be good to have these explained in a central place.

[Anton-4]

Some concepts that would be nice to have a short roc oriented explanation of:

• [ ] canonicalization
• [ ] arena allocation
• [ ] Abstract Syntax Tree AST
• [ ] implicit import
• [ ] reference count
• [x] platform
• [ ] compiler frontend
• [ ] compiler backend
• [ ] surgical linking
• [ ] legacy linker
• [ ] type inference
• [ ] type constraining
• [ ] ability
• [ ] IR: intermediate representation
• [ ] exhaustiveness checking
• [ ] code gen (=generation)
• [ ] interning
• [ ] type unification
• [ ] parsing
• [ ] in-place mutation
• [ ] immutable
• [ ] monomorphization
• [ ] region
• [ ] target
• [x] host
• [ ] type solving
• [ ] lambda set
• [ ] closure
• [ ] glue code
• [ ] anonymous function
• [ ] vendoring code
• [ ] thunk