update readme

README.md

@@ -1,4 +1,28 @@
 # pastebin
 
-## Themes
+a simple and lightweight pastebin service written in go and templ
+
+## Usage
+
+```
+$ ./pastebin
+
+Usage: pastebin [-addr <port>] [-max-size <size>]
+
+Options:
+  -addr string
+    	port to listen on (default ":3000")
+  -max-size int
+    	maximum size of a paste in bytes (default 32kB)
+```
+
+## Highlighting
+
+To get syntax highlighting, you must add the file extension at the end of your paste URL: `/<paste_id>.<extension>`
+
+Supported languages can be found [here](https://github.com/alecthomas/chroma/tree/master?tab=readme-ov-file#supported-languages)
+
+### Themes
+Themes can be applied by specifying in the URL: `/<paste_id>.<extension>/<theme>`
+
 [List of available themes](https://github.com/alecthomas/chroma/tree/master/styles)