[feature] Configurable list of mime-types that make the system just return a checksum (good for watching binary files)

Sometimes I just want to watch an `.exe` file and know if it changed
or sometimes I want to know if a `.jpeg` file changed

Could be super handy to have a config text-area that has a list of mimetypes

```
application/vnd.microsoft.portable-executable
application/executable
image/jpeg
```

When the fetcher hits that mimetype, it should not process the content, but just return the md5 checksum in the content-view

that way it could be configured for lots of interesting watching options, that arent just web-pages

Start by tracing the fetcher path that receives a response MIME type and the content-view path that displays processed content. Review how watch configuration is currently stored and exposed, then define the configured MIME-type behavior so matching binary responses show an MD5 checksum instead of processed content. Done means the setting accepts the listed MIME types and matching files are represented by their checksum.

Written by the indexing model from the issue text.