Set version to v2.2.1

Author: mvanbrab

main/src/version.js

@@ -1,5 +1,5 @@
 // Maintain the version string on the development branch:
 // - during development: set to (unreleased);
 // - right before merging to the main branch for making a new release: set to the new release tag (see https://github.com/SolidLabResearch/miravi-a-linked-data-viewer/tags).
-const version = "(unreleased)";
+const version = "v2.2.1";
 export default version;