Allow inline horizontal alignment of BBText

[vanscheijen]

The original pixi-multistyle-text seems to be archived, so I could not provide this patch upstream.

This patch will use the "align" style value of the first character of each line, to determine horizontal alignment per line.

This also fixes: https://forum.gdevelop.io/t/bbcode-allignment-does-not-work/75551

[vanscheijen]

This is the actual patch to the original (but unmaintained) codebase: tleunen/pixi-multistyle-text@cf96f8e

I've translated that patch to this compressed version, so the actual change (if you use a word-diff) is:

[-e,s=o[t];switch(this.withPrivateMembers()._style.align){case"left":e=d+c;break;case"center":e=d+c+(a-n[t])/2;break;case"right":e=d+c+a-n[t]}for(let-]

{+e,s=o[t];switch(s[0].style.align){case"left":e=d+c;break;case"center":e=d+c+(a-n[t])/2;break;case"right":e=d+c+a-n[t]}for(let+}