Add support for fully offline binary via compile-time 'offline' tag (#272)

* Add support for fully offline binary via compile-time 'offline' tag

* Update docs

client/lib/net.go

@@ -0,0 +1,16 @@
+//go:build !offline
+// +build !offline
+
+package lib
+
+import (
+	"net/http"
+)
+
+func GetHttpClient() *http.Client {
+	return http.DefaultClient
+}
+
+func IsOfflineBinary() bool {
+	return false
+}