update readme

Author: anthony-nhs

README.md

@@ -235,6 +235,26 @@ For an image built locally, you should put the IMAGE_VERSION=local-build.
 For an image built from a pull request, you should put the IMAGE_VERSION=<tag of image as show in pull request job>.  
 You can only use images built from a pull request for testing changes in github actions.   
 
+## Using images in github actions
+To use the image in github actions, you can use it in github actions using code like this
+```
+jobs:
+  my_job_name:
+    runs-on: ubuntu-22.04
+    container:
+      image: ghcr.io/nhsdigital/eps-devcontainers/<container name>:githubactions-<tag>
+      options: --user 1001:1001
+    steps:
+      - name: copy .tool-versions
+        run: |
+          cp /home/vscode/.tool-versions "$HOME/.tool-versions"
+      ... other steps ....
+```
+It is important that 
+- the image uses the tag starting githubactions-
+- there is `options: --user 1001:1001` below image
+- the first step copies .tool-versions from /home/vscode to $HOME/.tool-versions
+
 ## Generating a .trivyignore file
 You can generate a .trivyignore file for known vulnerabilities by either downloading the json scan output generated by the build, or by generating it locally using the scanning images commands above with a make target of scan-image-json
 
@@ -255,7 +275,7 @@ poetry run python \
 ```
 
 ## Common makefile targets
-There are a set of common Makefiles that are defined in `src/base/.devcontainer/makefiles` and are included from `common.mk`. These are installed to all built container images.
+There are a set of common Makefiles that are defined in `src/base/.devcontainer/Mk` and are included from `common.mk`. These are installed to /usr/local/share/eps/Mk on the base image so are available for all containers.
 
 This should be added to the end of each projects Makefile to include them
 ```