chore: create a dangerfile.ts and check for definition.json modific…

…ation

dangerfile.ts

@@ -0,0 +1,13 @@
+import { danger, markdown } from 'danger';
+
+const modifiedDefinitionJson = danger.git.fileMatch('src/theme/definition.json');
+
+if (modifiedDefinitionJson.edited) {
+  markdown(`
+Hey dear reviewer, I'm the Gravitee.io bot :robot:
+
+I just want to tell you that \`definition.json\` has been updated in this PR. As this file is used to theme clients' portals you should carefully review it to avoid any regression!
+
+Also, after merging this PR, you should update the \`definition.json\` of [APIM Rest API](https://github.com/gravitee-io/gravitee-management-rest-api).
+`);
+}