[DevEx] Add RFC template (#6173)

* [DevEx] Add RFC template

* Address Maayan's feedback

.github/ISSUE_TEMPLATE/devex_rfc.md

@@ -0,0 +1,25 @@
+---
+name: "\U0001FA90 DevEx RFC"
+about: Open a Request for Comments (RFC) for DevEx improvements
+title: "[DevEx RFC] "
+labels: DevEx
+assignees: ''
+---
+
+<!-- See an example RFC here: https://github.com/aptos-labs/aptos-core/issues/6171 -->
+
+## Context
+
+<!-- Include links to relevant RFCs, issues, and discussions. -->
+
+## Motivation
+
+<!-- This section should summarize the problem the RFC aims to address. Specific examples are encouraged. -->
+
+## Proposals
+
+<!-- Given this is an RFC and not a direct proposal, you are encouraged to propose multiple solutions to the problem to stimulate discussion. Naturally, the RFC creator will have their own opinion about which solution is best. This is fine, just make sure to explain your reasoning, e.g. with pros / cons / examples. -->
+
+## FAQ
+
+<!-- This is expected to be a living section that the RFC creator will update throughout the course of the RFC. This way, people new to the RFC can catch up quickly on discussions that have previously occurred. Feel free to start this off with questions you anticipate. -->