Update issue templates

Author: nbransby

.github/ISSUE_TEMPLATE/increase-api-coverage.md

@@ -0,0 +1,12 @@
+---
+name: Increase API Coverage
+about: Request for implementation of missing APIs
+title: Add [class name].[function name] to [library name] for [platform names]
+labels: API coverage
+assignees: ''
+
+---
+
+| Library                 | Class                                | Member                                          | Platforms                   |
+| :-------------------| :-------------------------- | :------------------------------------- | :---------------------- |
+| e.g auth               | e.g FirebaseAuth             | e.g signInWithGithub                      | e.g Android, iOS        |