Add precommit hook

[programmiri]

About this change - What it does

Introduces husky and lint-staged to run scripts on pre-commit if there are changes in coral.

Resolves: #112

Why this way

• prepare script in package.json is needed in this form ('cd .. && husky install coral/.husky') because .git folder is not on the same level as the package.json (see documentation)
• adds lint-staged page to enable us to control which scripts have to run dependent on where a file changes:
  • right now we only need to run the linting pre-commit hooks on changes in TypeScript and TSX files, since we have no linting for markdown etc.
• in pre-commit is a check to see if the staged files are in the coral directory, so we don't run tests when something outside coral changes.

[SmuliS]

Couple of things:

1. move lint-staged depedency under coral.
2. Couple of trivial comments in the actual pre-commit file

Lets also keep our minds open for https://pre-commit.com/, which clould also establish a base for git hooks for Java changes.

[SmuliS]

Is a general personal note: I would have not introduced lint-staged as a depedency as I think similar behaviour can be achieved with bash tooling.

[programmiri]

Is a general personal note: I would have not introduced lint-staged as a depedency as I think similar behaviour can be achieved with bash tooling.

Adding here what we decided about this in a call to be transparent:

• we will leave lint-staged for now, because it improves readability to enable others to get an overview about the processes more quick when compared to bash scripts
• we'll come back to the topic pre-commit-hooks later and check out pre-commit, which looks like a promising tool to only have one place where we define things while being very readable 💃