Feat/typescript migration

[sroucheray]

Hi @mrin9,

So here is the branch where I migrated the project to Typescript.

• Migrate all files from JS to TS
  • Use openapi-types lib wherever possible
  • Add extra typings where it was feasible
  • Cast to typing where some type incompatibility may arise
  • When I had not other way I added some anys where typing were difficult to understand
  • Try NOT to fix code yet, unless typings made it impossible to compile
  • Migrate rapidoc-mini.js (commented out for now to avoid extra work)
• Update tsconfig and webpack to adapt the build pipeline (commands did not change)
  • build passes and produces artefacts (js and typing files)

The remaining tasks I see

• Improve / Cleanup custom typings by someone who has more knowledge about the shape of object
  • Cleanup code wherever typings alert
  • Replace remaining any references in the code by proper types
  • Replace remaining 'as ...' type casting added in the code because of lack of knowledge about objects shapes or union types were not properly discriminated in the original code.
  • Check // TODO: Typescript migration... in the code to find mistake in original code now catched by the Typescript compiler (usually it needs refactor or removal)
• Testing
• Rebase on master and integrate last modification
• Simplify and make some portions of code more robust which should be much easier with the help of typings
• Add unit tests

One note about functions. You'll see that many functions have a first parameter named this, it's not a real parameter but the way typescript make it clear on which type of object the function is called (as many utility functions are called with call). https://www.typescriptlang.org/docs/handbook/2/functions.html#declaring-this-in-a-function

Example

...
export default function jsonSchemaViewerTemplate(this: RapiDocJSONSchemaViewerElement, isMini = false) {
...

[sroucheray]

Side note: my last commit is a fix for the response status not properly set when an error occurred. I encountered this error while working on a specific API. I took the opportunity to narrow down the type of the responseStatus to success | error instead of a string. Typescript makes it clear what this property can hold as a value now !

[sroucheray]

I merged master in my branch to keep up to date with latest commits