Only limited set Content Types available in autodetect mechanism

### What feature do you want to see added?

https://github.com/jenkinsci/google-storage-plugin/blob/4ef5d39ee2e235153085731665604f70cccf737e/src/main/java/com/google/jenkins/plugins/storage/AbstractUpload.java#L97

On upload, this plugin tries to guess file content type from extension and set Content Type header accordingly. However, only web-based formats are included in the mechanism.

Suggestion: let's add wider set of MIME types there. Our particular use case is for video/mp4.

### Upstream changes

_No response_

Start with the content-type autodetection logic in src/main/java/com/google/jenkins/plugins/storage/AbstractUpload.java around line 97. Review how extensions are mapped, then broaden the supported MIME types to include the reported video/mp4 case; done means uploads receive the appropriate Content-Type for that extension.

Written by the indexing model from the issue text.