message: docs: add `imageLambda` configuration info
diff: @@ -388,7 +388,7 @@ The exhaustive list of AWS actions required for a deployment:
  ### Lambda At Edge Configuration
  -Both **default** and **api** edge lambdas will be assigned 512mb of memory by default. This value can be altered by assigning a number to the `memory` input
  +The **default**, **api**, and **image** (for Next.js Image Optimization) edge lambdas will be assigned 512mb of memory by default. This value can be altered by assigning a number to the `memory` input
  ```yml
  # serverless.yml
  @@ -399,7 +399,7 @@ myNextApplication:
  memory: 1024
  ```
  -Values for **default** and **api** lambdas can be separately defined by assigning `memory` to an object like so:
  +Values for **default**, **api**, and **image** lambdas can be separately defined by assigning `memory` to an object like so:
  ```yml
  # serverless.yml
  @@ -410,6 +410,7 @@ myNextApplication:
  memory:
  defaultLambda: 1024
  apiLambda: 2048
  + imageLambda: 2048
  ```
  The same pattern can be followed for specifying the Node.js runtime (nodejs12.x by default):
  @@ -423,6 +424,7 @@ myNextApplication:
  runtime:
  defaultLambda: "nodejs10.x"
  apiLambda: "nodejs10.x"
  + imageLambda: "nodejs12.x" # Note that the sharp image library is built for NodeJS 12.x
  ```
  Similarly, the timeout by default is 10 seconds. To customise you can:
  @@ -436,11 +438,12 @@ myNextApplication:
  timeout:
  defaultLambda: 20
  apiLambda: 15
  + imageLambda: 15
  ```
  Note the maximum timeout allowed for Lambda@Edge is 30 seconds. See https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/lambda-requirements-limits.html
  -You can also set a custom name for **default** and **api** lambdas - if not the default is set by the [aws-lambda serverless component](https://github.com/serverless-components/aws-lambda) to the resource id:
  +You can also set a custom name for **default**, **api**, and **image** lambdas - if not the default is set by the [aws-lambda serverless component](https://github.com/serverless-components/aws-lambda) to the resource id:
  ```yml
  # serverless.yml
  @@ -451,6 +454,7 @@ myNextApplication:
  name:
  defaultLambda: fooDefaultLambda
  apiLambda: fooApiLambda
  + imageLambda: fooImageLambda
  ```
  ### Architecture
  