README: add description

README.md

@@ -1,3 +1,17 @@
 # minecraft-heatmap
 
-What the player doin?
+What the player doin?
+
+## What is this?
+
+This project is meant to visualize the login history of our minecraft server.
+It does this by:
+
+1. Regularly scanning through all the minecraft logs for login and logout messages.
+2. Calculating the intervals (as well as filtering invalid login/logout spans)
+3. Putting them into an sqlite database
+4. Fetching the data from the database, and displaying them on a website.
+
+It's intended to mimick the github contribution heatmap:
+
+![](https://preview.redd.it/dude-is-a-pro-v0-mltqiyxfjy291.jpg?auto=webp&s=f0ff6d458317d1023f82afb4db44717e4a8af42d)