Support `index.mjs` and `index.js` entrypoints

[littledivy]

Currently index.handler only works with index.ts. index.mjs support will make this layer work OOTB with open-next build outputs

[igorzi]

This should already work by setting Lambda HANDLER_EXT env variable to mjs.

[lucacasonato]

This repo is now archived because we are discontinuing the AWS Lambda layer for Deno. Instead we recommend you use a Docker image on AWS Lambda to run Deno. You can find a full guide in the docs.