📝 Added readme

Author: tofran

README.md

@@ -0,0 +1,23 @@
+# Advent of code leaderboard notifier
+
+Send a webhook notification when someone from an Advent Of Code leaderboard solves a puzzle
+
+I'm using this to track the progress of a group of friends on Discord.
+
+## Usage
+
+Just run this image periodically (at a minimum interval of 15 min):
+
+```sh
+$ docker run \
+  -e WEBHOOK_URL="your webhook url" \
+  -e ADVENT_OF_CODE_SESSION_ID="your advent of code session id" \
+  -e ADVENT_OF_CODE_LEADERBOARD_ID="numeric leaderboard id" \
+  -e CACHE_FILE=/cache/cache.json \
+  -v "$(pwd)/cache/:/cache/" \
+  ghcr.io/tofran/advent-of-code-leaderboard-notifier
+```
+
+## License
+
+MIT