Add AWS Lambda adapter

[fwang]

The solid-start-aws adapter allows to deploy the server function to both AWS Lambda and Lambda@Edge. This adapter takes a standard Lambda event payload, and returns a standard Lambda response.

For context, we created a SolidStartSite construct in SST that allows users to deploy SolidStart apps to AWS. An example looks like:

new SolidStartSite(stack, "web", {
  path: "path/to/my/solid/start/app"
});

If the PR gets merged, we will be able to launch the SolidStartSite. After that, I can submit a PR adding examples to the README.md/doc if fit.

Thanks for reviewing the PR!

^ btw, #181 can be closed