[html] completions for src, link, href...

[yuu2lee4]

add path choose window for img src、link href、script src、background-img src

[zbandhan]

It should also work for 'action' attribute of 'form' tag.
<form action="">

[octref]

I've compiled a list

// Selected from https://stackoverflow.com/a/2725168/1780148
const HTML_TAG_AND_ATTRIBUTE_WITH_URL_VALUE: { [tag: string]: string | string[] } = {
	// HTML 4
	a: 'href',
	body: 'background',
	del: 'cite',
	form: 'action',
	frame: ['src', 'longdesc'],
	img: ['src', 'longdesc'],
	ins: 'cite',
	link: 'href',
	object: 'data',
	q: 'cite',
	script: 'src',
	// HTML 5
	audio: 'src',
	button: 'formaction',
	command: 'icon',
	embed: 'src',
	html: 'manifest',
	input: 'formaction',
	source: 'src',
	track: 'src',
	video: ['src', 'poster']
};