Add Web Share types

[saschanaz]

Fixes microsoft/TypeScript#18642.

[orta]

Thanks @saschanaz

[Artur-]

The suggestion in the linked issue suggests adding

interface Navigator {
  share?: NavigatorShare;
}

however this PR adds it as

interface Navigator {
  share: NavigatorShare;
}

As share is not available in most browsers, you want to check for the existence of it before using it but

if (navigator.share) {

now results in an error

This condition will always return true since the function is always defined. Did you mean to call it instead? ts(2774)

[samtgarson]

@orta This comment 👆 seems correct, is there a reason share is always defined here?

[orta]

That is how the w3c spec defines it- you're welcome to send a PR making it optional 👍🏻

[ferm10n]

any reason why canShare wasn't added as well?

[saschanaz]

It's added later by #1125.