docs: Update feature_request.md (#1788)

* Update feature_request.md

Closes #1654

* Update feature_request.md

Co-authored-by: Alexander Courtis <alex@courtis.org>

.github/ISSUE_TEMPLATE/feature_request.md

@@ -9,6 +9,10 @@ assignees: ''
 **Is this a question?**
 Please start a new [Q&A discussion](https://github.com/nvim-tree/nvim-tree.lua/discussions/new) instead of raising a feature request.
 
+**Can this functionality be implemented utilising API?**
+nvim-tree exposes extensive API (see `:h nvim-tree-api`). Can it be used to achieve your goal? Is there a missing API that would make it possible?
+Given stable status of nvim-tree it's preferred to add new API than new functionality.
+
 **Is your feature request related to a problem? Please describe.**
 A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]