CDK Construct for adding config.json file to a Lambda Function

When using Lambda@Edge, a function cannot use environment variables.
This CDK Construct uses a Custom Resource to inject a config.json
file with user provided values into an existing function, and
publishes a new version that is ready to be used as part of a
CloudFront Distribution.

Inspired by similar mechanism in https://github.com/aws-samples/cloudfront-authorization-at-edge/

Usage

``bash
npm install @liflig/cdk-lambda-config
`

Using the construct:

`ts
const originalFunction = lambda.Function.fromFunctionArn(...)
const updatedFunction = new LambdaConfig(this, "UpdatedFunction", {
function: originalFunction,
config: {
Key1: "Some value",
Nested: {
Key2: "Other value",
},
},
nonce: "1", // See TSDoc.
})
// Can now retrieve the new version:
updatedFunction.version
`

Read from within the handler:

`ts
const fs = require("fs")
const path = require("path")
const config = JSON.parse(
fs.readFileSync(path.join(__dirname, "config.json"), "utf-8"),
)
``