Upgrade eslint + flow, and fix failed test from nullishCoalescingOperator (facebookarchive#2083)

Summary:
**Summary**

I want to upgrade ESLint and Flow on this project. I ended up with
- Remove unused `eslint-plugin-relay`
- Upgrade all ESLint packages to the latest version and fix all the new lint errors afterward.
  - `eslint-config-fbjs`
  - `eslint-config-prettier`
  - `eslint-plugin-babel`
  - `eslint-plugin-flowtype`
  - `eslint-plugin-jsx-a11y`
  - `eslint-plugin-prettier`
  - `eslint-plugin-react`

- Upgrade Flow (`flow-bin`) to the `0.115.0`.

~Then I found that `yarn test` is failing at~
```
src/component/handlers/composition/__tests__/DraftEditorCompostionHandler-test.js: Support for the experimental syntax 'nullishCoalescingOperator' isn't currently enabled (70:40)
```
~So I added `babel/plugin-proposal-nullish-coalescing-operator` to jest preprocessor as well.~
Move plugins in `.babelrc` to jest preprocessor as facebookarchive#2083 (comment)

**Test Plan**

`yarn lint`, `yarn flow`, and `yarn test` should all pass.
Pull Request resolved: facebookarchive#2083

Reviewed By: claudiopro

Differential Revision: D19398251

Pulled By: mrkev

fbshipit-source-id: 4fc2f6dd6e0cd44266d061455b7b6a433231715a

Author: lukyth

.babelrc

@@ -53,17 +53,16 @@
     "cross-env": "^6.0.3",
     "del": "^5.1.0",
     "es6-shim": "^0.35.5",
-    "eslint": "^6.6.0",
+    "eslint": "^6.8.0",
     "eslint-config-fbjs": "^3.1.1",
-    "eslint-config-prettier": "^6.5.0",
+    "eslint-config-prettier": "^6.9.0",
     "eslint-plugin-babel": "^5.3.0",
-    "eslint-plugin-flowtype": "^4.3.0",
+    "eslint-plugin-flowtype": "^4.6.0",
     "eslint-plugin-jsx-a11y": "^6.2.3",
-    "eslint-plugin-prettier": "^3.1.1",
-    "eslint-plugin-react": "^7.16.0",
-    "eslint-plugin-relay": "^1.3.12",
+    "eslint-plugin-prettier": "^3.1.2",
+    "eslint-plugin-react": "^7.17.0",
     "fbjs-scripts": "^1.2.0",
-    "flow-bin": "^0.110.1",
+    "flow-bin": "^0.115.0",
     "gulp": "^4.0.2",
     "gulp-babel": "^8.0.0",
     "gulp-clean-css": "^4.2.0",

meta/bundle-size-stats/Draft.js.json

@@ -15,6 +15,10 @@ module.exports = {
   process(src, filename) {
     var options = {
       presets: [fbjsConfigurePreset({rewriteModules: {map: moduleMap}})],
+      plugins: [
+        require('@babel/plugin-proposal-nullish-coalescing-operator'),
+        require('@babel/plugin-proposal-optional-chaining')
+      ],
       filename: filename,
       retainLines: true,
     };

meta/bundle-size-stats/Draft.min.js.json

@@ -50,4 +50,4 @@ unsafe-getters-setters
 ; nonstrict-import
 
 [version]
-^0.110.1
+^0.115.0

package.json

@@ -29,6 +29,8 @@ function editOnBlur(editor: DraftEditor, e: SyntheticEvent<HTMLElement>): void {
   // opposed to clicking to another tab or window).
   const {ownerDocument} = e.currentTarget;
   if (
+    // This ESLint rule conflicts with `sketchy-null-bool` flow check
+    // eslint-disable-next-line no-extra-boolean-cast
     !Boolean(editor.props.preserveSelectionOnBlur) &&
     getActiveElement(ownerDocument) === ownerDocument.body
   ) {