Improve Qute self-closing tags support

[fbricon]

In a Qute template, if you start typing {#inclu and select completion, the following is inserted:

{#include template}

{/include} 

It'd be nice to remove the closing tag if the user adds the self-closing slash after the template name ({#include template /}), while the tag content is empty, akin to self-closing tag behavior in vscode-xml.

There might be other specific tags where auto-close might be relevant (#insert? #fragment? ...), @mkouba or @FroMage may have some ideas

[FroMage]

That's a good idea, and valid for every tag.

[fbricon]

@FroMage I doubt this would be wanted in the case of control flow statements ({#if}, {#for} ...)

[FroMage]

Well, those always have bodies. But all the tags that have a / to close them without body need to have their closing tag removed.

[angelozerr]

@FroMage I doubt this would be wanted in the case of control flow statements ({#if}, {#for} ...)

Indeed, we ned to check if section tags has nested content (for user tag the html file includes {nested-content, we use already this information for completion with user tag)

I think it would be nice too to process the remove of /

When we remove this character, it should generate the end tag section.