Allow Negative Spacing In Bitmap Fonts

[AristurtleDev]

Description

While the BMFont file spec shows that the SpacingHoriz and SpacingVert values are bytes, and the angle code bitmap font generator does not allow setting negative spacing values, other tools like LibGDX Hiero do allow negative spacing, and users can edit the files manually.

This PR adds support to the BMFont file parsing to allow negative spacing values and also updates the rendering to take spacing into account when rendering glyphs for both horizontal and vertical spacing.

Related Issues/Tickets

• Closes MonoGame.Extended won't load .fnt files with negative spacing #1074
• Closes [Feature Request]: BMFont spacing values are not actually used in rendering #1078

Changes Made

• Changed SpacingHoriz and SpacingVert to use sbyte as type instead of byte to allow negative values
• Added new constructor to BitmapFont class that passes in line height, line spacing, and letter spacing
• Updated BitmapFont.GetStringRectangle to account for line spacing
• Property render BMFonts with letter and line spacing

Checklist

Please read and check the following items. Pull requests will not be reviewed if all items are not checked.

• I have verified that there are no existing pull requests that would overlap with this pull request.
• I have verified that I am following the guidelines as outlined in this project's contribution policy
• I have verified that this pull request adheres to this project's code of conduct.
• I have written a descriptive title for this pull request.
• I have provided appropriate test coverage were applicable.