Documenting Gem update (#797)

* Documenting Gem update

Added steps to upgrade a Gem in the Gemfile

* amended README to include running tests before and after Gem update

* Commit changes made by code formatters

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

README.md

@@ -146,7 +146,7 @@ For information on how to perform the data import before network cutover, please
 
 ## Site Import from CSV
 
-Details of how to perform a new [Site Import from CSV](docs/site_import_from_csv.md). 
+Details of how to perform a new [Site Import from CSV](docs/site_import_from_csv.md).
 
 ## CI/CD
 
@@ -158,3 +158,32 @@ Details of how to perform a new [Site Import from CSV](docs/site_import_from_csv
 ## Known Issues
 
 -   Dependabot currently does not support a container image monitoring solution only for the [Docker container](Dockerfile) _ruby:3.2.2-alpine3.16_, this alpine images needs to be updated manually.
+
+## Updating Gems
+
+Developer tools (alpine-sdk, ruby-dev) have been added to the container to facilitate Gem version updates. To update a Gem version:
+
+-   Build and run tests to make sure you have a baseline of the application running well.
+
+-   Build the dev container
+
+```bash
+  make build-dev
+```
+
+-   Run the application with an interactive shell
+
+```bash
+  make shell-dev
+```
+
+-   Change the version in the Gemfile
+-   In the interactive shell run a bundle update for the Gem being updated, e.g.
+
+```bash
+  bundle update rails
+```
+
+-   Check that the Gemfile.lock has the new version
+
+-   Destroy container, re-build and run tests.