add CONTRIBUTING.md file

Author: msukkari

CONTRIBUTING.md

@@ -0,0 +1,40 @@
+## Build from source
+>[!NOTE]
+> Building from source is only required if you'd like to contribute. The recommended way to use Sourcebot is to use the [pre-built docker image](https://github.com/sourcebot-dev/sourcebot/pkgs/container/sourcebot).
+
+1. Install <a href="https://go.dev/doc/install"><img src="https://go.dev/favicon.ico" width="16" height="16"> go</a>, <a href="https://nodejs.org/"><img src="https://nodejs.org/favicon.ico" width="16" height="16"> NodeJS</a>, [redis](https://redis.io/), and [postgres](https://www.postgresql.org/). Note that a NodeJS version of at least `21.1.0` is required.
+
+2. Install [ctags](https://github.com/universal-ctags/ctags) (required by zoekt)
+    ```sh
+    // macOS:
+    brew install universal-ctags
+
+    // Linux:
+    snap install universal-ctags
+    ```
+
+3. Clone the repository with submodules:
+    ```sh
+    git clone --recurse-submodules https://github.com/sourcebot-dev/sourcebot.git
+    ```
+
+4. Run `make` to build zoekt and install dependencies:
+    ```sh
+    cd sourcebot
+    make
+    ```
+
+    The zoekt binaries and web dependencies are placed into `bin` and `node_modules` respectively.
+
+5. Create a copy of `.env.development` and name it `.env.development.local`. Update the required environment variables.
+
+6. If you're using a declerative configuration file (the default behavior if you didn't enable auth), create a configuration file and update the `CONFIG_PATH` environment variable in your `.env.development.local` file.
+
+7. Start Sourcebot with the command:
+    ```sh
+    yarn dev
+    ```
+
+    A `.sourcebot` directory will be created and zoekt will begin to index the repositories found in the `config.json` file.
+
+8. Start searching at `http://localhost:3000`.