webui: recognize AsciiDoc files as valid text files

[jhradilek]

Similarly to Markdown, AsciiDoc is essentially a plain text format and models typically have no problem extracting information from it. Currently, the web UI does not list AsciiDoc files among supported file types in the file dialog, and reports the following error for them:

Unsupported File Types

README.adoc
File type not supported

This pull request adds support for AsciiDoc files to the web UI. It uses the most commonly used .adoc file extension and the text/asciidoc MIME type as recommended in the AsciiDoc FAQ.

[allozaur]

Looking good, please just add a static webui build to the PR and we're good to go!

[jhradilek]

Thank you, I just pushed the static build as requested. I used npm run build as described in the web UI README file. Should I also include updated package-lock.json with the static build?