feat: multiple borders

[Tropix126]

Depends on #836.

• Removes the border_align attribute.
  • This was necessary to do since individual borders can have their own alignments. Also, since the border style argument can only be solid or none anyways, this seemed reasonable.
  • If more styles other than solid (dashed, dotted, etc...) are eventually added (adding these at this point would be pretty ridiculously complex) they can be added as an optional argument e.g. 1 inner dotted red.
  • Replaces the redundant <style> field with alignment intead. Syntax is now <width> <width?> <width?> <width?> <align> <fill> e.g. 1 inner red.
• Adds support for styling multiple borders on a single rect (similar to how shadow already works).

rect {
    width: "80",
    height: "80",
    corner_radius: "2",
    background: "rgb(0, 0, 0)",
    border: "6 outer red, 5 outer orange, 4 outer yellow, 3 outer green, 2 outer blue, 1 outer purple",
    margin: "8"
}

[marc2332]

Lovely.