docs: Add prettier support

Official guidelines:
https://prettier.io/docs/en/install.html
https://prettier.io/docs/en/integrating-with-linters.html
https://github.com/prettier/eslint-config-prettier

Steps taken:
npm install --save-dev --save-exact prettier
Create .prettierignore
Create .prettierrc.js
npm install --save-dev eslint-config-prettier
Edit .eslintrc.js

docs/.eslintrc.js

@@ -5,7 +5,12 @@ module.exports = {
     es2021: true,
     node: true,
   },
-  extends: ["eslint:recommended", "plugin:react/recommended"],
+  extends: [
+    "eslint:recommended",
+    "plugin:react/recommended",
+    "prettier",
+    "prettier/react",
+  ],
   parserOptions: {
     ecmaFeatures: {
       jsx: true,