Cosmetic: add option for space in self-closing tag

[FloEdelmann]

In self-closing tags, there is no space before the slash (<tag/> instead of <tag />). I know this is purely cosmetic, but I prefer having a space there.

It would be nice to be able to control this behaviour with an option.

Bonus: The option could also add a space in the XML header: <?xml version="1.0" encoding="UTF-8" ?> instead of <?xml version="1.0" encoding="UTF-8"?>

[soumak77]

This would be very useful when using this library to modify a cordova config.xml. Cordova uses a space before the closing tag. As a result, any minor changes with this library looks like a massive rewrite to the file since every line is included in the diff.

[soumak77]

@oozcitak this feature is broken. Instead of adding a space, it adds the word true.

    <content src="index.html"true/>
    <access origin="*"true/>
    <allow-navigation href="http://ionic.local/*"true/>
    <allow-navigation href="http://192.168.1.226:8100"true/>
    <allow-intent href="http://*/*"true/>
    <allow-intent href="https://*/*"true/>
    <allow-intent href="tel:*"true/>
    <allow-intent href="sms:*"true/>
    <allow-intent href="mailto:*"true/>
    <allow-intent href="geo:*"true/>

[soumak77]

@oozcitak I expected the spacebeforeslash option to accept true or false, however, this yields the results above. If I set the option to ' ' then it works as expected.

[oozcitak]

This is by design. It requires the string to be inserted before the closing slash. See the wiki: https://github.com/oozcitak/xmlbuilder-js/wiki#converting-to-string

[oozcitak]

I am adding a check for boolean true as well: 63d5143