deps: ignore dependabot for peer dependencies (jaredpalmer#904)

- several of the dependencies in the tree are only there because they
  are peerDeps, and not because we directly depend on them
  - they should only be upgraded in tandem with the dep(s) they are
    peers of and pretty much never in isolation

- Greenkeeper made several PRs for peers which previously caused an
  erroneous/buggy update of `@types/jest` to 25 many months before Jest
  was upgraded to 25
  - and honestly those Greenkeeper PRs for peers had confused me a
    good deal too

.github/dependabot.yml

@@ -14,6 +14,20 @@ updates:
       # only upgrade prod deps (not devDeps)
       - dependency-name: '*'
         dependency-type: production
+    ignore:
+      # ignore eslint-config-react-app's peerDeps
+      - dependency-name: '@typescript-eslint/eslint-plugin'
+      - dependency-name: '@typescript-eslint/parser'
+      - dependency-name: 'babel-eslint'
+      - dependency-name: 'eslint-plugin-flowtype'
+      - dependency-name: 'eslint-plugin-import'
+      - dependency-name: 'eslint-plugin-jsx-a11y'
+      - dependency-name: 'eslint-plugin-react'
+      - dependency-name: 'eslint-plugin-react-hooks'
+      # ignore Jest's "peers" that should be upgraded simultaneously with Jest
+      - dependency-name: '@types/jest'
+      - dependency-name: 'jest-watch-typeahead'
+      - dependency-name: 'ts-jest'
     # temporarily disable dep upgrade PRs for / as they're being updated
     open-pull-requests-limit: 0