docs: add a custom domain

apps/docs/docs/editor/custom-domain.md

@@ -0,0 +1,19 @@
+# Add a custom domain
+
+You can bind a custom domain to your typebot in the "Share" tab.
+
+<img
+  src="/img/custom-domain/add-domain.png"
+  width="700"
+  alt="Add my domain button"
+/>
+
+To connect a new domain, follow the instructions:
+
+<img
+  src="/img/custom-domain/instructions.png"
+  width="700"
+  alt="Add domain instructions"
+/>
+
+Once you've added the corresponding DNS record, click on the "Save" button. You might have to wait for a few minutes before the record is properly propagated.