Enable minimal typechecking for src/sidebar/services. Note that most
service factories are missing parameter documentation, so their usage is
not checked.

 - Fix up JSDoc errors and omissions in `src/sidebar/services`
 - Add types for the `tiny-emitter` npm module. The module does ship
   with its own types, but doesn't specify the types for the default
   export
 - Add additional properties to `Annotation`, `Group` and `Profile` API objects