Sort out whitespace between text and HTML nodes

[ehrencrona]

This solves the issue of whitespace either being wrongly added or removed inside inline tags or between text and tags.

See the description for #116 on which it builds. In addition to the examples mentioned there, it fixes more cases involving extraneous or removed whitespace. See examples below. It is, however, a much bigger rewrite than #116, so I suspect this PR might get turned down on the basis of being too radical a change. I'm therefore opening this as a separate PR so that merging just #116 is still an option.

Apart from fixing more issues, I also find the code in this PR cleaner.

In addition to the fixes mentioned in #116 it fixes #58 fully.

It also handles for example:

<a href=""><i>link</i></a>

where it used to add a whitespace inside the <a>...</a> tag to make

<a href="">
    <i>link</i>
</a>

---

You might not want whitespace before or after {#if} blocks, such as with this (somewhat contrived) code that prints item* for new items and item! for updated ones:

{#each items as item}
    <b>{item.name}</b>{#if item.isNew}*{/if}{#if item.isUpdated}!{/if}
{/each}

which used to be formatted as

{#each items as item}
    <b>{item.name}</b>
    {#if item.isNew}*{/if}
    {#if item.isUpdated}!{/if}
{/each}

thereby printing item * and item !. (Add a space or newline before each {#if} and they will still be placed on separated lines)

---

It used to turn

<div>
    <b>one</b>,<b>two</b>
</div>

into

<div>
    <b>one</b>
    ,
    <b>two</b>
</div>

(thereby adding whitespace around the comma). with this PR the result is

<div>
    <b>one</b>,<b>two</b>
</div>

---

It used to remove manually added empty lines between text and tags, so e.g.

<div>

<Tag />
Text
<Tag />

Text

<Tag />


Text


<Tag />


</div>

would become

<div>

    <Tag />
    Text
    <Tag />
    Text
    <Tag />
    Text
    <Tag />

</div>

but is now

<div>
    <Tag />
    Text
    <Tag />

    Text

    <Tag />

    Text

    <Tag />
</div>

(note that the empty lines right inside the <div>...</div> are also removed)

[dummdidumm]

This is really fantastic work! I have some small code-style change requests, but that's all 👍

[ehrencrona]

@dummdidumm Thanks for the review! I've applied the changes you suggested and also reformatted print/index.ts (I didn't want to do it earlier to not mess up the diff).

[dummdidumm]

🎉