Add BorderLabels to Border widget

[CosmicPredator]

Added BorderLabels to Border Widget to show text inline along the borders. Currently, it has the following alignment options,

• Top Left
• Top Center
• Top Right
• Bottom Left
• Bottom Center
• Bottom Right

Here is a screenshot,

Example code snippet,

self.border.labels = &[_]vxfw.Border.BorderLabel {
    .{ .text = "TopLeft", .alignment = .TopLeft },
    .{ .text = "TopCenter", .alignment = .TopCenter },
    .{ .text = "TopRight", .alignment = .TopRight },
    .{ .text = "BottomLeft", .alignment = .BottomLeft },
    .{ .text = "BottomCenter", .alignment = .BottomCenter },
    .{ .text = "BottomRight", .alignment = .BottomRight },
};

[rockorager]

This is a good feature to add. Approach is good but you just need to make sure you are working on graphemes vs bytes.

[CosmicPredator]

@rockorager I have made the changes requested.
Btw, thanks for the helper snippets, really appreciate it 😃.

[rockorager]

One remaining issue on the loop.

[CosmicPredator]

@rockorager Done. (I think I need to get a good grasp on grapheme iterator)