Update README with instructions for use

README.md

@@ -16,3 +16,23 @@ gleam add finch_gleam
 ```
 
 and its documentation can be found at <https://hexdocs.pm/finch_gleam>.
+
+## Usage
+
+```gleam
+import gleam/uri
+import gleam/http
+import gleam/http/request
+import gleam/erlang/atom
+import finch
+
+assert Ok(url) = uri.parse("https://example.com/")
+assert Ok(req) = request.from_uri(url)
+let req = request.Request(..req, method: http.Post, body: "foo bar")
+
+// Build Finch request from gleam/http request
+let finch_req = finch.build(req, [])
+
+// Run request with Finch, using Finch.Server, returns gleam/http response
+assert Ok(resp) = finch.request(finch_req, atom.create_from_string("Elixir.Finch.Server"))
+```