docs: Add GovCloud layer info (#5414)

* docs: Add GovCloud layer info

* formatting change

* change formatting for headers

---------

Co-authored-by: Simon Thulbourn <sthulb@@users.noreply.github.com>

Author: sthulb

docs/index.md

@@ -72,6 +72,26 @@ You can install Powertools for AWS Lambda (Python) using your favorite dependenc
     | x86_64          | __arn:aws:lambda:{region}:017000801446:layer:AWSLambdaPowertoolsPythonV3-{python_version}-x86_64:2__{: .copyMe}:clipboard:       |
     | ARM          | __arn:aws:lambda:{region}:017000801446:layer:AWSLambdaPowertoolsPythonV3-{python_version}-arm64:2__{: .copyMe}:clipboard: |
 
+=== "Lambda Layer (GovCloud)"
+
+    [Lambda Layer](https://docs.aws.amazon.com/lambda/latest/dg/configuration-layers.html){target="_blank"} is a .zip file archive that can contain additional code, pre-packaged dependencies, data,  or configuration files. We compile and optimize [all dependencies](#install), and remove duplicate dependencies [already available in the Lambda runtime](https://github.com/aws-powertools/powertools-lambda-layer-cdk/blob/d24716744f7d1f37617b4998c992c4c067e19e64/layer/Python/Dockerfile#L36){target="_blank"} to achieve the most optimal size.
+
+    For the latter, make sure to replace `{python_version}` without the period (.), e.g., `python312` for `Python 3.12`.
+
+    **AWS GovCloud (us-gov-east-1)**
+
+    | Architecture | Layer ARN                                                                                                 |
+    | ------------ | --------------------------------------------------------------------------------------------------------- |
+    | x86_64          | __arn:aws-us-gov:lambda:us-gov-east-1:165087284144:layer:AWSLambdaPowertoolsPythonV3-{python_version}-x86_64:2__{: .copyMe}:clipboard:       |
+    | ARM          | __arn:aws-us-gov:lambda:us-gov-east-1:165087284144:layer:AWSLambdaPowertoolsPythonV3-{python_version}-arm64:2__{: .copyMe}:clipboard: |
+
+    **AWS GovCloud (us-gov-west-1)**
+
+    | Architecture | Layer ARN                                                                                                 |
+    | ------------ | --------------------------------------------------------------------------------------------------------- |
+    | x86_64          | __arn:aws-us-gov:lambda:us-gov-west-1:165093116878:layer:AWSLambdaPowertoolsPythonV3-{python_version}-x86_64:2__{: .copyMe}:clipboard:       |
+    | ARM          | __arn:aws-us-gov:lambda:us-gov-west-1:165093116878:layer:AWSLambdaPowertoolsPythonV3-{python_version}-arm64:2__{: .copyMe}:clipboard: |
+
     === "AWS Console"
 
         You can add our layer using the [AWS Lambda Console _(direct link)_](https://console.aws.amazon.com/lambda/home#/add/layer){target="_blank"}: