Fall back to GitHub CLI for local authentication (#23)

If GITHUB_TOKEN is not defined, this will query the `gh` utility for a
PAT, so the index can be generated locally without passing the env
variable to the command.

scripts/generate-index-json.ts

@@ -20,6 +20,7 @@ import type {
     Application,
 } from '../site/src/schema';
 import { ParsedOrgFile, readOrgIndexFiles } from './orgFiles';
+import { execSync } from 'child_process';
 
 const nordicOrgs: string[] = ['nrfconnect', 'nordic', 'nordicplayground'];
 const partnerOrgs: string[] = ['golioth'];
@@ -29,7 +30,8 @@ function notUndefined<T>(value: T | undefined): value is T {
 }
 
 function initialiseGitHubApi() {
-    const authToken = process.env.GITHUB_TOKEN;
+    const authToken =
+        process.env.GITHUB_TOKEN ?? execSync('gh auth token', { encoding: 'utf-8' }).trim();
 
     if (!authToken) {
         throw new Error(