Add openApp method

[Kudo]

open is good to facilitate cross platform opening. sometimes i just want to open an application without specifying url or file target. the concept is something like open(null, { app: { name: open.apps.chrome }});. this pr just introduces an openApp api. please help to review if the concept makes sense.

[Kudo]

thanks @sindresorhus. these review comments are neat and i should update all. please take a look when you get a chance.

[sindresorhus]

Missing the description from index.d.ts

[sindresorhus]

Can you manually verify that these changes do not break normal usage of open?

[Kudo]

thanks for kindly helping with these wordings.

Can you manually verify that these changes do not break normal usage of open?

i did execute ava to test cases in test.js, anything else recommended to further test?

[sindresorhus]

open/test.js

Lines 4 to 7 in e21e623

	// Tests only checks that opening doesn't return an error
	// it has no way make sure that it actually opened anything.
	// These have to be manually verified.

[Kudo]

i did go through the test cases one by one in macos. there are just two cases with pipe not opening anything. that's same with main branch and open does not encode target in macos.

open/test.js

Lines 57 to 63 in e21e623

	test('open URL with query strings and pipes', async t => {
	await t.notThrowsAsync(open('https://sindresorhus.com/?abc=123&def=456&ghi=w|i|t|h'));
	});
	test('open URL with query strings, spaces, pipes and a fragment', async t => {
	await t.notThrowsAsync(open('https://sindresorhus.com/?abc=123&def=456&ghi=w|i|t|h spaces#projects'));
	});

[Kudo]

thank you, @sindresorhus. you are awesome to have these cool libraries.