Update Getting Started optional tools section with latest Node14 Docker images

[meryllblanchet]

https://github.com/AdobeDocs/project-firefly/blob/main/src/pages/getting_started/index.md

1. Node10 and Node12 images are mentioned, but Node14 images should be preferably used.
2. The documentation could be clearer about when to download the images manually (e.g. on slow connections).

[shazron]

adobeapiplatform/adobe-action-nodejs-v10 is at 3.0.28 now
adobeapiplatform/adobe-action-nodejs-v12 is at 3.0.28 now
adobeapiplatform/adobe-action-nodejs-v14 is at 3.0.28 now

[shazron]

Related: adobe/aio-cli-plugin-app#481

[elagun]

It should also be noted in the Optional Tools section that these Docker image need not be pulled manually. They will be downloaded and run automatically by the CLI when running aio app:run --local.

Especially the part "The following commands must be executed to install the required Docker images" should be removed because it's not correct. In fact the CLI will most probably download a different version and not use the Docker image that you downloaded manually at all. For example, I manually downloaded v14:3.0.28 and then running the local development the CLI ignored this image and downloaded and ran v14:3.0.26