S3 Bucket Deployments with content encoding based on file extension.

Currently, there is **contentEncoding?:string** option in **BucketDeployment** construct (System-defined content-encoding metadata to be set on all objects in the deployment). It would be nice to have possibility to specify contentEncoding according to mapping for file extension. Example: for files with extension **.br** specify "Content-Encoding: br", for **.gzip** files - "Content-Encoding: gzip" and so on.

### Use Case

We use s3+ cloudfront pair to serve static website. To provide better performance **br** files are server based on **Accept-Encoding** header, so our files have to copies (ex: **index.html** and **index.html.br***). Currently, we have to use aws cli to deploy differently encoded files with right headers. If **BucketDeployment** construct will support **contentEncoding** encoding by file extension option, it would be more easy-to-go static hosting option.

* [ ] :wave: I may be able to implement this feature request
* [ ] :warning: This feature might incur a breaking change

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This is a :rocket: Feature Request

Start by locating the BucketDeployment construct and its existing contentEncoding option, then trace how deployment objects receive metadata. Define how file-extension mappings should be configured and applied for extensions such as .br and .gzip, and verify that differently encoded files receive the expected S3 Content-Encoding values.

Written by the indexing model from the issue text.