Added prettier (without formatting the repo)

Author: mattpocock

.prettierignore

@@ -0,0 +1,3 @@
+tmp
+dist
+.changeset

package.json

@@ -13,7 +13,8 @@
     "test": "jest && npm run test-types",
     "test-types": "tsc --noEmit -p ./tests/tsconfig.tests.json",
     "lint": "eslint ./src --ext .ts",
-    "format": "prettier --write 'src/**/*.ts?(x)' && npm run lint -- --fix",
+    "format": "prettier --write . && npm run lint -- --fix",
+    "format-check": "prettier --check .",
     "typecheck": "tsc --noEmit",
     "clean": "rm -rf ./dist ./tmp",
     "build": "npm run clean && rollup --config && mv tmp/*.js dist",