update readme

README.md

@@ -1,2 +1,26 @@
 # minhttpd
 tiny http server, made to mimic* the usability of "python -m http.server"
+
+by default, will serve from "/var/www" on port 8000, you can mount a volume here or change the path.
+
+## usage
+
+### default root
+```sh
+docker run --rm -p 8000:8000 -v $(pwd):/var/www arson.pw/minhttpd
+```
+
+### custom root
+```sh
+docker run --rm -p 8000:8000 -v $(pwd):/tmp arson.pw/minhttpd --chdir /tmp
+```
+
+### custom port (method 1)
+```sh
+docker run --rm -p 1337:8000 -v $(pwd):/var/www arson.pw/minhttpd
+```
+
+### custom port (method 2)
+```sh
+docker run --rm -p 1337:1337 -v $(pwd):/var/www arson.pw/minhttpd --port 1337
+```