add .github-token to gitignore and add additional info in build instructions

Author: msukkari

.gitignore

@@ -41,4 +41,6 @@ next-env.d.ts
 
 .sourcebot
 /bin
-/config.json
+/config.json
+
+.github-token

README.md

@@ -128,14 +128,14 @@ Sourcebot also supports indexing GitLab & BitBucket. Checkout the [index.json](.
 
 ## Building Sourcebot
 
-0. Install <a href="https://go.dev/"><img src="https://go.dev/favicon.ico" width="16" height="16"> go</a> and <a href="https://nodejs.org/"><img src="https://nodejs.org/favicon.ico" width="16" height="16"> NodeJS</a>
+1. Install <a href="https://go.dev/doc/install"><img src="https://go.dev/favicon.ico" width="16" height="16"> go</a> and <a href="https://nodejs.org/"><img src="https://nodejs.org/favicon.ico" width="16" height="16"> NodeJS</a>. Note that a NodeJS version of at least `21.1.0` is required.
 
-1. Clone the repository with submodules:
+2. Clone the repository with submodules:
     ```sh
     git clone --recurse-submodules https://github.com/TaqlaAI/sourcebot.git
     ```
 
-2. Run make to build zoekt and install dependencies:
+3. Run make to build zoekt and install dependencies:
     ```sh
     cd sourcebot
     make