chore: extract v3 into its own repository (#16131)

These should be the necessary changes to move v3 source code & issues to the new home for Ionic 3: https://github.com/ionic-team/ionic-v3

.github/ISSUE_TEMPLATE.md

@@ -4,8 +4,7 @@
 
 **Ionic version:**  (check one with "x")
 (For Ionic 1.x issues, please use https://github.com/ionic-team/ionic-v1)
-[ ] **2.x**
-[ ] **3.x**
+(For Ionic 2.x & 3.x issues, please use https://github.com/ionic-team/ionic-v3)
 [ ] **4.x**
 
 **I'm submitting a ...**  (check one with "x")

.github/PULL_REQUEST_TEMPLATE.md

@@ -7,6 +7,6 @@
 -
 -
 
-**Ionic Version**: 1.x / 2.x / 3.x / 4.x
+**Ionic Version**:
 
 **Fixes**: #

.github/ionic-issue-bot.yml

@@ -82,8 +82,6 @@ noReply:
 
 labelPullRequest:
   labels:
-    - label: v3
-      branch: v3
     - label: angular
       branch: master
       path: ^angular
@@ -94,6 +92,14 @@ labelPullRequest:
 
 wrongRepo:
   repos:
+    - label: "ionitron: v3"
+      repo: ionic-v3
+      message: >
+        Thanks for the issue! We have moved the source code and issues for Ionic 3 into a separate repository.
+        I am moving this issue to the repository for Ionic 3. Please track this issue over there.
+
+
+        Thank you for using Ionic!
     - label: "ionitron: cli"
       repo: ionic-cli
       message: >