Shareable links should get preloaded by default

[lidel]

When user takes a screenshot or imports files via OS integration, we copy a shareable link to clipboard. However, the content is not present on gateway node until someone requests it, and that leads to bad UX (https://github.com/ipfs-shipyard/ipfs-desktop/issues/1604#issuecomment-707274675).

IPFS Companion sends HTTP HEAD request to trigger data preload.

I believe Desktop should do the same by default, but there needs to be an option to disable preload, in case user wants to avoid non-IPFS traffic coming from their machine.

[jessicaschilling]

"Preload Shareable Links" in the prefs menu could look like below. Note that this mockup also contains the other cube menu amendments currently outstanding in the Desktop issue queue ... that menu is getting a bit lengthy but that may be a separate item for consideration.