Add prettier config (#176)

Copy over Speedometer's prettier config which tries to follow WebKit's style guide for the most part except:
- Single block statements are on the same line
- Braces are required to force a new line for block statements

Author: camillobruni

.prettierignore

@@ -0,0 +1,33 @@
+.*
+node_modules
+package-lock.json
+dist
+build
+*bundle*.js
+third_party
+
+/Octane/*
+/ARES-6/*
+/cdjs/*
+/8bitbench/*
+/class-fields/*
+/code-load/*
+/SunSpider
+/SeaMonster
+/WSL
+/worker/bomb-subtests
+/wasm/dotnet/build-*
+/wasm/tfjs-model-*
+/simple/*
+/generators/*
+/threejs/*
+
+# Ignore everything in RexBench, then selectively un-ignore.
+/RexBench/*
+!/RexBench/*/
+/RexBench/*/*
+!/RexBench/*/benchmark.js
+
+!benchmark.js
+!*/benchmark.js
+!/**/*.md

.prettierrc

@@ -0,0 +1,12 @@
+{
+    "arrowParens": "always",
+    "bracketSameLine": false,
+    "bracketSpacing": true,
+    "htmlWhitespaceSensitivity": "css",
+    "printWidth": 100,
+    "semi": true,
+    "singleQuote": false,
+    "tabWidth": 4,
+    "trailingComma": "es5",
+    "useTabs": false
+}

package-lock.json

@@ -20,6 +20,7 @@
         "decompress": "node utils/compress.mjs -d -k",
         "lint:check": "eslint **/*.{js,mjs,jsx,ts,tsx}",
         "pretty:check": "prettier --check ./",
+        "pretty:format": "prettier --write ./",
         "format:check": "npm run pretty:check && npm run lint:check",
         "test:chrome": "node tests/run-browser.mjs --browser chrome",
         "test:firefox": "node tests/run-browser.mjs --browser firefox",
@@ -43,7 +44,7 @@
         "http-server": "^14.1.1",
         "jsvu": "^2.5.1",
         "local-web-server": "^5.4.0",
-        "prettier": "^2.8.3",
+        "prettier": "^2.8.8",
         "selenium-webdriver": "^4.35.0"
     },
     "dependencies": {