Add an RRFC issue template (#3)

Author: justinfagnani

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,5 @@
+blank_issues_enabled: true
+contact_links:
+  - name: RFC
+    url: https://github.com/lit/rfcs/edit/main/rfcs/0000-rfc-template.md
+    about: To open a formal RFC, make a PR that copies the issue template linked here to a new file named with the format `NNNN-descriptive-name.md`. See [Opening an RFC](https://github.com/lit/rfcs#opening-an-rfc) for more details.

.github/ISSUE_TEMPLATE/rrfc.md

@@ -0,0 +1,34 @@
+---
+name: RRFC
+about: Requesting Request For Comment. If you have an idea for an RFC and want to get feedback before opening a formal RFC, use this issue template to describe your idea.
+title: '[RRFC] <title>'
+assignees:
+labels:
+---
+
+- [ ] I searched for an existing RRFC which might be relevant to my RRFC
+
+## Motivation
+<!--
+Why do you want this feature or change?
+-->
+
+### Example
+<!--
+Example(s) of what this proposal would change - code or behavior.
+-->
+
+### How
+
+#### Current Behaviour
+
+#### Desired Behaviour
+
+### References
+<!--
+Examples:
+* Related to #0
+* Depends on #0
+* Blocked by #0
+-->
+* n/a