Merge pull request #13 from tskit-dev/master-main

master->main

Author: benjeffery

README.md

@@ -19,7 +19,7 @@ via the following git commands from within your forked repository:
 
 ```
 $ git fetch upstream
-$ git checkout upstream/master # note this switches to a 'detached HEAD' state
+$ git checkout upstream/main # note this switches to a 'detached HEAD' state
 $ git checkout -b my-topic-branch
 # Do work and add commits.
 $ git push origin my-topic-branch
@@ -37,4 +37,4 @@ project under the OSS license of the relevant repository (e.g.
 as specified in the LICENSE file in the root of the repository).
 
 ---
-<div style="text-align: right">Logo courtesy of Tom Shirley</div>
+<div style="text-align: right">Logo courtesy of Tom Shirley</div>