Add airburst distance offset

[Keshash]

Additions

Describe new functionality added by your code, e.g.

• Adds a new field for airburst projectiles: airburstDistanceOffset, which allows saying "explode 10 tiles before reaching the target" in xml.

Reasoning

Why did you choose to implement things this way, e.g.

• Improves angled aerial explosions

Alternatives

Describe alternative implementations you have considered, e.g.

Testing

Check tests you have performed:

• Compiles without warnings
• Game runs without errors
• (For compatibility patches) ...with and without patched mod loaded
• Playtested a colony (specify how long)

[github-actions]

You can download the rebuilt assembly for this PR here: https://combatextended.lp-programming.com/CombatExtended-17296282476.zip

[github-actions]

You can download the rebuilt assembly for this PR here: https://combatextended.lp-programming.com/CombatExtended-20480860989.zip

[N7Huntsman]

Works in my testing. Included adjustments to the frag angle to take advantage of the change. We'll likely also discuss increasing airburst frag count in the near future, but that's beyond the scope of this PR.

[github-actions]

You can download the rebuilt assembly for this PR here: https://combatextended.lp-programming.com/CombatExtended-20493464082.zip

[github-actions]

You can download the rebuilt assembly for this PR here: https://combatextended.lp-programming.com/CombatExtended-20493603817.zip

[Safairette]

It works. Though as noted, needs numbers tweaks to frag count to properly saturate the affected angle.

[github-actions]

You can download the rebuilt assembly for this PR here: https://combatextended.lp-programming.com/CombatExtended-20499595502.zip