Changing most references in our codebase from master to main

Signed-off-by: Joe Tursi <[email protected]>

.github/CONTRIBUTING.md

@@ -63,6 +63,6 @@ project, please refer to:
 ---
 
 [0]: https://developercertificate.org/
-[1]: https://github.com/chapel-lang/chapel/tree/master/doc/rst/developer/bestPractices/DCO.rst
+[1]: https://github.com/chapel-lang/chapel/tree/main/doc/rst/developer/bestPractices/DCO.rst
 [2]: https://chapel-lang.org/contributing.html
-[3]: https://github.com/chapel-lang/chapel/tree/master/doc/rst/developer/bestPractices/ContributorInfo.rst
+[3]: https://github.com/chapel-lang/chapel/tree/main/doc/rst/developer/bestPractices/ContributorInfo.rst

.github/ISSUE_TEMPLATE.md

@@ -35,7 +35,7 @@ If an input file is required, include it as well. -->
 **Associated Future Test(s):**
 <!-- Are there any tests in Chapel's test system that demonstrate this issue?
      e.g. [`test/path/to/foo.chpl`](
-           https://github.com/chapel-lang/chapel/blob/master/test/path/to/foo.chpl
+           https://github.com/chapel-lang/chapel/blob/main/test/path/to/foo.chpl
           ) #1234 -->
 
 ### Configuration Information

.github/workflows/CI.yml

@@ -2,7 +2,7 @@ name: CI
 
 on:
   push:
-    branches: [ master ]
+    branches: [ main ]
   pull_request:
 
 env: