Build & push updated Docker image to `webportal-service`

[grantfitzsimmons]

In this milestone, we updated major dependencies for the web portal (see #6310), but we never updated the images on Docker Hub.

We need to push this to both the improve-build and latest tags:
https://hub.docker.com/r/specifyconsortium/webportal-service/tags

As another nice feature, we also will support image captions on the thumbnail view for images (specify/webportal-installer#77) as a new optional attribute. This can be added by setting displayImgCaption to true in the configuration json file.

[acwhite211]

Built and pushed new web-portal docker image to Docker Hub.