Isaiah Becker-Mayer

See https://github.com/vector-im/hydrogen-web/commit/295edfc7fcab9cedce0d9e6783feba7b328792ea for what amounts to a proposed direction for typing Matrix API responses. The rest of the changes type `Sync.js` --> `Sync.ts` plus any incidental changes required in that...

Conversion for all the objects that according to the README are meant to extend `IGridItemViewModel`

Credit to @DanilaFe for the assist (https://github.com/DanilaFe/microui/blob/master/src/observable/list/SortedMapList.ts) in converting `SortedMapList` to ts.

This was probably the most challenging conversion so far, as it deals with api level events which I'm not well versed in, and some of which aren't already well defined...

And cleans up elsewhere