add recommended workflow for copier updates (#214)

Add recommended workflow for copier updates

Co-authored-by: Gary Yendell <gary.yendell@diamond.ac.uk>

---------

Co-authored-by: Tom C (DLS) <101418278+coretl@users.noreply.github.com>
Co-authored-by: Gary Yendell <gary.yendell@diamond.ac.uk>

Author: 3 people

docs/how-to/update-template.md

@@ -1,5 +1,7 @@
 # How to update to the latest template structure
 
+## Overview
+
 To track changes to the upstream template, run
 
 ```
@@ -15,3 +17,24 @@ git diff --check
 ```
 
 Once they are all fixed, make a commit.
+
+## Recommended Workflow
+
+The following steps are recommended to update your project, especially for infrequently updated projects:
+
+- first make sure all the tools are updated to latest versions
+    - for devcontainers
+        - `ctrl+shift+p` -> `Remote-Containers: Rebuild Without Cache and Reopen in Container`
+    - for local development
+        - `pip install -e .[dev] --force-reinstall`
+- validate your project against the latest tools
+    - `tox -p`
+- fix issues found by the above
+- commit the changes
+- update the template
+    - `copier update --trust`
+- fix any merge conflicts
+- validate that the project still works
+    - `tox -p`
+- fix any issues found by the above
+- commit the changes