Link to main branch of .github

This has already been moved to `main`. So update the link.

CODE_OF_CONDUCT.md

@@ -2,4 +2,4 @@
 
 For the Zarr project's code of conduct, please see:
 
-https://github.com/zarr-developers/.github/blob/master/CODE_OF_CONDUCT.md
+https://github.com/zarr-developers/.github/blob/main/CODE_OF_CONDUCT.md

CORE_DEV_GUIDE.md

@@ -25,7 +25,7 @@ after approval before merge to ensure that other core developers have a reasonab
 chance to weigh in.
 
 You may of course also continue to make your own pull requests as before and in accordance
-with the [general contributor guide](https://github.com/zarr-developers/.github/blob/master/CONTRIBUTING.md).
+with the [general contributor guide](https://github.com/zarr-developers/.github/blob/main/CONTRIBUTING.md).
 These pull requests require the approval of another core developer before they can be merged.
 
 We are also an international community, with contributors from many different time zones,
@@ -35,7 +35,7 @@ schedules and working habits, even if it slows the project down slightly - we ar
 for the long run. In the same vein you also shouldn't feel pressured to be constantly
 available or online, and users or contributors who are overly demanding and unreasonable
 to the point of harassment will be directed to our
-[Code of Conduct](https://github.com/zarr-developers/.github/blob/master/CODE_OF_CONDUCT.md).
+[Code of Conduct](https://github.com/zarr-developers/.github/blob/main/CODE_OF_CONDUCT.md).
 We value sustainable development practices over mad rushes.
 
 When merging, use GitHub's
@@ -133,8 +133,8 @@ that responsibility seriously.
 As a core member, you should be familiar with community and developer
 resources such as:
 
--  Our [contributor guide](https://github.com/zarr-developers/.github/blob/master/CONTRIBUTING.md).
--  Our [code of conduct](https://github.com/zarr-developers/.github/blob/master/CODE_OF_CONDUCT.md).
+-  Our [contributor guide](https://github.com/zarr-developers/.github/blob/main/CONTRIBUTING.md).
+-  Our [code of conduct](https://github.com/zarr-developers/.github/blob/main/CODE_OF_CONDUCT.md).
 -  Our [governance](GOVERNANCE.md).
 -  [PEP8](https://www.python.org/dev/peps/pep-0008/) for Python style.
 -  [PEP257](https://www.python.org/dev/peps/pep-0257/) and the

GOVERNANCE.md

@@ -41,7 +41,7 @@ all are encouraged to do so. By contributing to the project, community members
 can directly help to shape its future.
 
 Potential contributors are encouraged to read the [Contributing Guide](http://zarr.readthedocs.io/en/stable/contributing.html)
-as well as the [Code of Conduct](https://github.com/zarr-developers/.github/blob/master/CODE_OF_CONDUCT.md).
+as well as the [Code of Conduct](https://github.com/zarr-developers/.github/blob/main/CODE_OF_CONDUCT.md).
 
 Anyone who has recently engaged with the project in these concrete ways, in compliance with
 the Contributing Guide and Code of Conduct, is considered a contributor and can request