format: install prettier

.prettierrc.json

@@ -0,0 +1,11 @@
+{
+    "printWidth": 80,
+    "tabWidth": 2,
+    "useTabs": false,
+    "semi": true,
+    "singleQuote": true,
+    "trailingComma": "none",
+    "bracketSpacing": false,
+    "arrowParens": "avoid",
+    "parser": "typescript"
+  }

package-lock.json

@@ -4296,6 +4296,12 @@
       "integrity": "sha1-IZMqVJ9eUv/ZqCf1cOBL5iqX2lQ=",
       "dev": true
     },
+    "prettier": {
+      "version": "1.18.2",
+      "resolved": "https://registry.npmjs.org/prettier/-/prettier-1.18.2.tgz",
+      "integrity": "sha512-OeHeMc0JhFE9idD4ZdtNibzY0+TPHSpSSb9h8FqtP+YnoZZ1sl8Vc9b1sasjfymH3SonAF4QcA2+mzHPhMvIiw==",
+      "dev": true
+    },
     "pretty-format": {
       "version": "24.9.0",
       "resolved": "https://registry.npmjs.org/pretty-format/-/pretty-format-24.9.0.tgz",

package.json

@@ -42,6 +42,7 @@
     "eslint": "^6.4.0",
     "jest": "^24.9.0",
     "jest-circus": "^24.9.0",
+    "prettier": "1.18.2",
     "ts-jest": "^24.1.0",
     "typescript": "^3.6.3"
   }