Add file index.d.ts

[riccardoscalco]

Related to hybridsjs/hybrids#173.

[riccardoscalco]

Some updates: I made a svelte app where to import and test <trend-line>. Note that the web-component module is installed from the local disk:

"dependencies": {
  "@nextbitlabs/trend-line": "file:../trend-line",
  ...
},

My first attempt was to add file index.d.ts in module trend-line as suggested in hybridsjs/hybrids#173:

declare global {
    interface HTMLElementTagNameMap {
        'trend-line': TrendLine;
    }
}

But, with or without file index.d.ts, I do not see any error. Should I expect any error or warning from TypeScript?

I noted there is a config file for TypeScript:

{
  "extends": "@tsconfig/svelte/tsconfig.json",

  "include": ["src/**/*"],
  "exclude": ["node_modules/*", "__sapper__/*", "public/*"]
}

I added the local path to module trend-line, but without success.

I definitively need to wrap my head around TS.

@nkint Do you have any suggestion?