[Feature Request]: Show last update date timestamp

### Prerequisites

- [x] I have searched existing issues to ensure this feature hasn't already been requested
- [x] I have tested using the latest version of docs-builder

### What problem are you trying to solve?

It would be good to show the last update date of each document, based on Git timestamps. For example:

### Proposed Solution

- Collect the git history at build.
- Produce the timestamp for each built document based on the git timestamp.

Not sure how this would work for reference docs though.

### Examples and Research

MkDocs and others do it based on git information: https://squidfunk.github.io/mkdocs-material/setup/adding-a-git-repository/#document-dates

### Alternative Solutions

_No response_

### Additional Context

_No response_

### How important is this feature to you?

Nice to have