Add script to automatically generate a declaration file for the JS API

[engbergandreas]

This PR adds a Python script to automatically generate a declaration file (.d.ts) for the JavaScript API. This give TypeScript syntax highlighting and intellisense for the entire API including the OpenSpace lua functions.

For now we keep the openspace-ai-js.d.ts file in this repository since it seems to be quite a process to add it to the npm @types and DefinitelyTyped repo since our Lua API is updated quite often, it will be nice to have more control over it.

Usage

Simply copy the openspace-api-js.d.ts file from the declaration folder to the src project folder, might have to update the compilerOptions to include the new file as well.

Generate an updated version

Run the Python script generatetypescriptfile.py from the root folder of openspace-api-js