Fix administration and development docs

docs/development/yarn-commands.md

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+# Yarn Commands
+
+The following commands are supported.
+You must set `NODE_ENV` to use these commands.
+To do so, you can add the following line to your `.env` file:
+
+```
+NODE_ENV=development
+```
+
+## Local dev server
+- `yarn dev` - Run the local dev server.
+
+## Building
+- `yarn build` - Compile without a dev server, into `/static` directory.
+
+## Translations
+- `yarn manage:translations` - Normalizes translation files. Should always be run after editing i18n strings.
+
+## Tests
+- `yarn test` - Runs all tests.
+
+- `yarn test:lint` - Runs all linter tests.
+
+- `yarn test:lint:js` - Runs only JavaScript linter.
+
+- `yarn test:lint:sass` - Runs only SASS linter.
+
+- `yarn test:jest` - Frontend unit tests.