CSS is missing when running without external sources

[m1ga]

In the template the local CSS is ignored when you build with --no-external-references:

slack-export-viewer/slackviewer/templates/viewer.html

Line 7 in 92fd281

{% if not no_external_references %}

The CSS should be treated as a local reference as it is a local file and not be excluded. There is only the font that is an external request. For DSGVO/GDPR reasons it should be pulled locally, removed or replaced with just

html {
    font-family: sans-serif;
}