[Docker] Update docker images declared in `action.yaml` files

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Feature description

Add option in dependabot to parse docker images declared in `action.yaml` files

Example file

```yml

runs:
using: 'composite'
steps:
- name: Run
shell: bash
run: >
docker run ubuntu@sha256:7a57c69fe1e9d5b97c5fe649849e79f2cfc3bf11d10bbd5218b4eb61716aebe6
```

Start by locating the Docker dependency parser and the action.yaml handling path. Use the provided composite-action example as the input case, then verify that the Ubuntu image digest in a docker run command is detected and can receive updates through Dependabot.

Written by the indexing model from the issue text.