Support per-link download attribute support in file link browser¶

The a[download] attribute has widespread support: https://caniuse.com/download

A partial solution exists with https://forge.typo3.org/issues/83285

However, this does not solve the problem of per-link (rather than per-FAL-file or per-fluid-template) enforced download.

Use case example:¶

Some file types, such as PDF, MP3 and MP4 can be displayed by the browser.

As a website author, editors want to be able to provide links to view / listen / watch in the browser, and alternative links to download the same PDF / MP3 / MP4 file.

This requires the download attribute to be editable in the RTE link browser, as well as - to a lesser extent (as fluid templates can be overridden for that use case) - other places where link browsers are used (link input fields).

Documentation:¶

https://developer.mozilla.org/en-US/docs/Web/HTML/Element/a#attributes

Proposal:¶

- Provide a checkbox in the link properties pane, such as
[ ] Force file download.
Result: <a href="..." download>...</a>

- When the checkbox is checked, provide an optional input field for the download file name.
[x] Force file download | Download as: [placeholder.pdf ]
Result if filled: <a href="..." download="custom-filename.pdf">...</a>