docs(issues): use Meta instead of Optional as suggested

* #174 (comment)

Author: myii

.github/ISSUE_TEMPLATE/bug_report.md

@@ -62,7 +62,7 @@ Notes:
 
 ---
 
-### Optional: How can this template be improved?
+### Meta: How can this template be improved?
 <!-- Feel free to suggest how this template can be improved. -->
 
 

.github/ISSUE_TEMPLATE/feature_request.md

@@ -36,7 +36,7 @@ Notes:
 
 ---
 
-### Optional: How can this template be improved?
+### Meta: How can this template be improved?
 <!-- Feel free to suggest how this template can be improved. -->