update README.md

README.md

@@ -1,2 +1,23 @@
 # Unshorten
 Firefox Extension and API server for revealing links behind shortened URLs.
+
+## Usage
+In order to deal with CORS, Unshorten must send links to a resolver API. 
+
+```shell
+cd server
+make build
+docker -d --name unshortener -p 8000:8000 unshortener-api
+```
+
+Build the extension and import into Firefox. Right click on a link and choose 
+"Unshorten Link". The result will be copied to the clipboard.
+
+```shell
+cd extension
+make zip
+```
+
+## Supported Sites
+- t.co
+- tinyurl.com

server/src/main.py

@@ -40,4 +40,4 @@ async def receive_url(url: Optional[str] = None):
         CACHE[url] = result
         return result
 
-    return {"error": f"server error"}
+    return {"error": "server error"}

server/src/unshorteners.py

@@ -1,7 +1,7 @@
 """Unshortening functions"""
 import re
-import requests
 from typing import Optional
+import requests
 
 
 def unshorten_tinyurl(url: str) -> Optional[str]: