Add test change proposal template

Author: jgraham

.github/ISSUE_TEMPLATE/test-change-proposal.md

@@ -0,0 +1,16 @@
+---
+name: Test Change Proposal
+about: Propose adding or removing tests for an Interop 2022 focus area
+title: ''
+labels: test-change-proposal
+assignees: ''
+
+---
+
+** Test List **
+
+* List tests here
+
+** Rationale **
+
+Justification for the changes.