fix safari input jumping

[tanhauhau]

Fix #3449

When we dynamically set input.value = value, browser will reset the cursor to the end of the input. However, if the input.value === value, most browser (except safari) will not reset the cursor.

so even the example below, when editing from the middle of the input, only in safari, the input cursor will jump to the end of input

<script>
	let value = '';
	function onInput(e) {
		value = e.target.value;
	}
</script>

<input {value} on:input={onInput} />

To fix this, we have to check whether input.value === value before setting it:

if (dirty & /*name*/ 1 && input.value !== /*name*/ ctx[0]) {
    input.value = /*name*/ ctx[0];
}

and we've already done that for bindings:

<script>
	let value = '';
</script>

<input bind:value>

[Conduitry]

Nice, yeah, this is the type of solution I was hoping for. It makes sense now why this was still happening if that previous fix was only for two-way binding.

It looks like neither this PR nor #2511/#3208 handle <textarea>s though - is this something that is needed?

[tanhauhau]

I tried textarea on desktop safari, it seems okay (not jumping) to me. 🙈
And we didn't check the case of contenteditable also....