add extra extensions to text editor app

[tralph3]

Description

Adds more extensions to the file manager app. The previous selection was quite sparse, leaving out a lot of common files. These additions should make it more universal. In the future, maybe it'd be better to rely on a text detection method, rather than extensions.

Types of changes

• Bugfix
• Enhancement (a change that doesn't break existing code or deployments)
• Breaking change (a modification that affects current functionality)
• Technical debt (addressing code that needs refactoring or improvements)
• Tests (adding or improving tests)
• Documentation (updates or additions to documentation)
• Maintenance (like dependency updates or tooling adjustments)

[JammingBen]

Looks good, thanks!

I'm waiting for the merge because we're currently in a hardening sprint for the upcoming stable release and this is technically a feature. I'll merge it once we have a stable branch.

In the future, maybe it'd be better to rely on a text detection method, rather than extensions.

I agree. The issue is that we need to rely on information the server gives us in the PROPFIND. Any (potentially expensive) text detection wouldn't work. Still, there are better ways to do this than via the file extension.