chore: add new issue template for CDE implementation requests

.github/ISSUE_TEMPLATE/new_cde.md

@@ -0,0 +1,23 @@
+---
+name: New CDE
+about: Add a new Data Harmonization Team-approved Common Data Element
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+**CDE name**
+
+**CDE number in caDSR, including version**
+
+**Deeplink to CDE in caDSR**
+
+**Harmonization discussion number for this CDE**
+
+**Link to Data Harmonization Team's implementation approval of this CDE**
+
+**Special notes or caveats when implementing this CDE**
+Anything unique about this CDE that the implementer should be aware of.
+For example, are we using only a subset of the caDSR values? Do the values have some unit?
+Are there a large number of possible values that we can't concisely enumerate?