Add instructions on how to run the game locally to README

README.md

@@ -1 +1,25 @@
-# IvarK.github.io
+# Antimatter Dimensions
+
+## Run
+
+To run the game locally, you will need to install
+[Node.js](https://nodejs.org/) (LTS suggested).
+
+First, run the following command in your terminal (or command line) while being
+inside the checked out repository:
+
+```
+npm install
+```
+
+After all the packages are installed, start up the game:
+
+```
+npm run serve
+```
+
+This will make the game served via your localhost, and the playable link will
+be displayed in your terminal. The server **doesn't** need to be restarted
+after you've made changes - just reload the page. The server **can**
+occasionally crash, so check your terminal from time to time and run `serve`
+again if needed.