feat: Add support for nodejs14.x

[pgrzesik]

This is an attempt to add support for nodejs14.x runtime. I believe it needs manual action from someone with proper privileges to actually build the base image - it also needs a bit more testing - currently, it follows a similar approach that was used when adding support for nodejs12.x.

I'd love to hear feedback, what is additionally needed and how I can help to get support for nodejs14.x through the finish line/

Thanks in advance

cc @mhart

Closes: #329

[azai91]

when can we merge these changes?

[pgrzesik]

@azai91 it needs manual action that will actually dump and upload the runtime. I'm no longer sure this is the best approach in general and a better idea might be to just use the images that AWS released recently

[arzke]

In our team, we've switched to amazon/aws-sam-cli-build-image-nodejs14.x:latest when upgrading to node 14. It's probably not worth the effort of maintaining this image anymore now that amazon provides official docker images for CI. But it would probably be a good idea to mention in the readme that we now recommend to use official amazon images?

[Kmink]

I would vote to merge this in.. We use Serverless (serverless.com) for organizing/test/deploying our serverless infrastructure, and they rely on the lambci/lambda images for local invocations. With no nodejs14.x images available, we can't test our lambda functions locally with that toolset. My hope is that they start to support the Amazon SAM images, but until they do, we're stuck. If this is a fairly straightforward addition, we would certainly appreciate it being made available.