[BREAKING] Refactor the entire build process

For https://github.com/vector-im/riot-web/issues/8880

Features:
* Export modern JS
* Export typings
* Export source maps that actually mean something
* No longer supporting minified builds

This is a step towards being a boring SDK and not anticipating an install location. 

This commit requires a major version bump of the SDK.

browser-index.js

@@ -31,5 +31,5 @@ if (indexedDB) {
     );
 }
 
-module.exports = matrixcs; // keep export for browserify package deps
+export default matrixcs; // keep export for browserify package deps
 global.matrixcs = matrixcs;