[DOCS] Update Github OAuth guide to contain 'User-Agent' in fetch hea…

…der (#1434)

Co-authored-by: pilcrow <[email protected]>

docs/pages/guides/oauth/account-linking.md

@@ -17,6 +17,7 @@ const tokens = await github.validateAuthorizationCode(code);
 const userResponse = await fetch("https://api.github.com/user", {
 	headers: {
 		Authorization: `Bearer ${tokens.accessToken}`
+		"User-Agent": "my-app", // GitHub requires a User-Agent header
 	}
 });
 const githubUser = await userResponse.json();