Format the spec with prettier (graphql#727)

* Formatting: add prettier

* Format markdown

Author: benjie

.github/ISSUE_TEMPLATE.md

@@ -2,10 +2,15 @@
 
 Before creating your issue:
 
-* Have a question? Find community resources at https://graphql.org/community/
+- Have a question? Find community resources at https://graphql.org/community/
 
-* Find an editing mistake? Create a Pull Request with the edited fix! The Github UI allows you to edit files directly, find the source files at: https://github.com/graphql/graphql-spec/tree/master/spec
+- Find an editing mistake? Create a Pull Request with the edited fix! The Github
+  UI allows you to edit files directly, find the source files at:
+  https://github.com/graphql/graphql-spec/tree/master/spec
 
-* Improvements to documentation? Head over to https://github.com/graphql/graphql.github.io
+- Improvements to documentation? Head over to
+  https://github.com/graphql/graphql.github.io
 
-* Feature request? First read https://github.com/graphql/graphql-spec/blob/master/CONTRIBUTING.md and prefer creating a Pull Request!
+- Feature request? First read
+  https://github.com/graphql/graphql-spec/blob/master/CONTRIBUTING.md and prefer
+  creating a Pull Request!

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,3 +1,4 @@
 !!! IMPORTANT !!!
 
-Please Read https://github.com/graphql/graphql-spec/blob/master/CONTRIBUTING.md before creating a Pull Request.
+Please Read https://github.com/graphql/graphql-spec/blob/master/CONTRIBUTING.md
+before creating a Pull Request.

.github/workflows/ci.yml

@@ -13,7 +13,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: actions/setup-node@v1
         with:
-          node-version: '16.x'
+          node-version: "16.x"
       - run: npm ci
       - run: npm test
   publish:
@@ -26,13 +26,13 @@ jobs:
           fetch-depth: 0
       - uses: actions/setup-node@v1
         with:
-          node-version: '16.x'
+          node-version: "16.x"
       - run: npm ci
       - run: npm run build
       - uses: peaceiris/actions-gh-pages@v3
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           keep_files: true
           cname: spec.graphql.org
-          user_name: 'github-actions[bot]'
-          user_email: 'github-actions[bot]@users.noreply.github.com'
+          user_name: "github-actions[bot]"
+          user_email: "github-actions[bot]@users.noreply.github.com"

.github/workflows/prettier.yaml

@@ -0,0 +1,12 @@
+name: Prettier formatting
+on: [push, pull_request]
+
+jobs:
+  build:
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-node@v1
+        with:
+          node-version: "16.x"
+      - run: npm ci
+      - run: npm run format:check

.prettierignore

@@ -0,0 +1,11 @@
+*.swp
+*~
+.*.haste_cache.*
+.DS_Store
+npm-debug.log
+/build
+/changelogs
+/out
+/gh-pages
+/node_modules
+/package.json