Add progressive web app support

[matthewkdies]

Clear and concise description of the problem

Using Podfetch on mobile is an incredibly common (if not the dominant) use case. But Podfetch doesn't have a standalone app, nor is that likely.

A great alternative would be a progressive web app, which allows opening websites as their own standalone "apps" on mobile. A combination of this (plus a new documentation page I would be happy to contribute to!) could give Podfetch an "app" feel, improving usability

Suggested solution

Implementing the standalone app from this guide would likely accomplish it, alongside custom icons, etc.

Alternative

No response

Additional context

No response

Validations

• [X] Follow our Code of Conduct
• [X] Read the Contributing Guide.
• [X] Check that there isn't already an issue that request the same feature to avoid creating a duplicate.