Upgrade to ESLint v7.x

Update eslint-config-hypothesis which was in turn holding back various
other ESLint packages.

The newest update to eslint-plugin-react-hooks found an incorrect usage
of `useCallback` in `ThreadCard` where `debounce` was being called on
ever render instead of only when certain dependencies changed.

package.json

@@ -42,12 +42,12 @@
     "enzyme-adapter-preact-pure": "^2.0.0",
     "escape-html": "^1.0.3",
     "escape-string-regexp": "^1.0.5",
-    "eslint": "^6.0.1",
-    "eslint-config-hypothesis": "^2.0.0",
+    "eslint": "^7.3.1",
+    "eslint-config-hypothesis": "^2.4.0",
     "eslint-plugin-jsx-a11y": "^6.2.3",
     "eslint-plugin-mocha": "^7.0.1",
     "eslint-plugin-react": "^7.12.4",
-    "eslint-plugin-react-hooks": "^3.0.0",
+    "eslint-plugin-react-hooks": "^4.0.4",
     "exorcist": "^1.0.1",
     "express": "^4.14.1",
     "fancy-log": "^1.3.3",

src/annotator/.eslintrc.js

+// eslint-disable-next-line
 'use strict';
 
 module.exports = {

src/sidebar/components/thread-card.js

 import classnames from 'classnames';
+import debounce from 'lodash.debounce';
 import { createElement } from 'preact';
-import { useCallback } from 'preact/hooks';
+import { useCallback, useMemo } from 'preact/hooks';
 
-import debounce from 'lodash.debounce';
 import propTypes from 'prop-types';
 import { closest } from '../../shared/dom-element';
 import useStore from '../store/use-store';
@@ -18,12 +18,12 @@ function ThreadCard({ frameSync, settings = {}, thread }) {
   const threadTag = thread.annotation && thread.annotation.$tag;
   const isFocused = useStore(store => store.isAnnotationFocused(threadTag));
   const showDocumentInfo = useStore(store => store.route() !== 'sidebar');
-
-  const focusThreadAnnotation = useCallback(
-    debounce(tag => {
-      const focusTags = tag ? [tag] : [];
-      frameSync.focusAnnotations(focusTags);
-    }, 10),
+  const focusThreadAnnotation = useMemo(
+    () =>
+      debounce(tag => {
+        const focusTags = tag ? [tag] : [];
+        frameSync.focusAnnotations(focusTags);
+      }, 10),
     [frameSync]
   );