Resolve "Type-checker doesn't use the global context" ✨️

Closes #17 🐔️👍️
Approved-by: belazy <aarthuur01@gmail.com>
Approved-by: loutr <loutr@crans.org>
Approved-by: aalbert <augustin.albert@bleu-azure.fr>

🦀️🍰🦀️🍰🦀️🍰

* chore: misc

* chore : add test coverage

* chore(kernel): Reduce code complexity

* fix(kernel): Made Context mutable

* fix(kernel): Made type_checker.rs full of reference

* fix(kernel): Made term.rs full of reference

* fix(kernel): Use of reference

* Apply 1 suggestion(s) to 1 file(s)

* Fix : refer to #19

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* Fix : remove unused trait

* Fix : apply suggestion

* Fix : use Self in impl

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* Chore: use `Environment::new()` instead of `Default::default()`

* Chore :  add documentation

* Chore : expand tests coverage

* Revert "Feat : parse Constants"

This reverts commit 0618fd79.

* Feat : move `Environment` to respective file

* Feat : add test for Env use during typechecking

* Feat : parse Constants

* Feat : use `Environment` during type-checking/inference

* Feat : add `GlobalContext`