Fix Typo in Proxy Environment Variables Heading (#766)

Update basics.md

Author: leopardracer

docs/src/basics.md

@@ -38,7 +38,7 @@ fuelup self update
 
 To configure `fuelup` to use your proxy setting you can change `http_proxy`(***other optional environments see below***) environment value. The value format is in [libcurl format](https://everything.curl.dev/usingcurl/proxies/type.html) as in `[protocol://]host[:port]`.
 
-### Supported proxy enviroment variables
+### Supported proxy environment variables
 
 - http_proxy
 - HTTP_PROXY