Feature/typescript support

[vahdet]

This PR introduces Typescript to the content of src directory in such ways:

• Added tsconfig.json and convert file extension from .js to .ts, then solve the typing problems. Introduced shared and isolated types/interfaces (Kept them detailed as possible, but left as any where I cannot figure out).

• Changed eslint configuration for Typescript .

• Removed Babel dependencies and .babelrc file, as the current structure do not need it (But, it may be tested more specifically).

• Converted the npm build command to tsc (See in package.json).

• Oh, finally, put the language notations code sections in markdown files to make them look better on (at least) the local IDEs.

[JamesBrill]

Many thanks for making these changes, @vahdet - I certainly learned something from reading them.

I must admit I wasn't expecting the library itself to be rewritten in TypeScript, just the addition of a declaration file. Is there any advantage to consumers of this library for it to be written in TypeScript? Or is a declaration file sufficient? We now have types defined under @types here.

I do not wish to undermine your efforts here, but if the declaration files in DefinitelyTyped are sufficient to enable simple integration of this library into TypeScript projects, then I would prefer it to remain vanilla JavaScript, mainly because I prefer to keep the build simple for development and the language one that I'm familiar with. That's not to say I don't see the benefits of TypeScript - I may choose to adopt it in future, in which case your PR here will serve as a fantastic starting point for making that migration.

[vahdet]

@JamesBrill You are right, this PR goes well beyond the adding TypeScript support as the types are added to the DefinitelyTyped by @OleksandrYehorov as stated here. All in all, this lib can now be used by TypeScript projects -which was the main motive.

And, yes, it can be a reference once you consider rather a TypeScript re-write. Thus, I do not think postponing/closing this PR is a loss of effort or such (I had already did the changes on my fork before deciding to send as a PR). So, feel free :)

[JamesBrill]

I'll close this PR and the issue as TypeScript consumers seem to be unblocked for now. Thanks for raising the issue and providing these changes for reference.