chore: separate install docs (#3859)

coder.env

@@ -1,9 +1,18 @@
-# Run "coder server --help" for flag information.
+# Coder must be reachable from an external URL
+# for users and workspaces to connect.
+
+# Option 1) Enable CODER_TUNNEL to generate a
+# unique *. try.coder.com access URL
+CODER_TUNNEL=false
+
+# Option 2) Set an access URL
+# e.g. https://coder.example.com
 CODER_ACCESS_URL=
+
 CODER_ADDRESS=
 CODER_PG_CONNECTION_URL=
 CODER_TLS_CERT_FILE=
 CODER_TLS_ENABLE=
 CODER_TLS_KEY_FILE=
-# Generate a unique *.try.coder.app access URL
-CODER_TUNNEL=false
+
+# Run "coder server --help" for flag information.