Enable typechecking of most JS files in src/annotator

Enable typechecking of most JS files in src/annotator except for:

 - The entrypoint index.js file. This cannot be usefully checked since
   it imports many CoffeeScript files
 - pdf-sidebar.js - This extends a class currently written in
   CoffeeScript
 - src/annotator/anchoring/pdf.js - This requires types for various
   PDF.js globals to be defined
 - The `annotator/plugin` directory

src/annotator/icons.js

+// @ts-nocheck
+
 /**
  * Set of icons used by the annotator part of the application via the `SvgIcon`
  * component.

src/annotator/plugin/pdf-metadata.js

@@ -30,7 +30,7 @@ export default class PDFMetadata {
    * Construct a `PDFMetadata` that returns URIs/metadata associated with a
    * given PDF viewer.
    *
-   * @param {PDFViewerApplication} app
+   * @param {Object} app - The `PDFViewerApplication` global from PDF.js
    */
   constructor(app) {
     this._loaded = new Promise(resolve => {

src/tsconfig.json

@@ -11,8 +11,11 @@
     "target": "ES2020"
   },
   "include": [
+    "annotator/*.js",
+    "annotator/anchoring/*.js",
     "annotator/config/*.js",
     "annotator/components/*.js",
+    "annotator/plugin/*.js",
     "annotator/util/*.js",
     "boot/*.js",
     "shared/*.js",
@@ -26,6 +29,14 @@
     "sidebar/store/*.js"
   ],
   "exclude": [
+    // Enable this once the rest of `src/annotator` is checked.
+    "annotator/index.js",
+
+    // Files in `src/annotator` that still have errors to be resolved.
+    "annotator/pdf-sidebar.js",
+    "annotator/anchoring/pdf.js",
+    "annotator/plugin/document.js",
+
     // Enable this once the rest of `src/sidebar` is checked.
     "sidebar/index.js",