Added lerp and lerp_smooth functions for math and 2D / 3D vectors

Fixes #[include number of issue this PR fixes - if any]

Summary of Changes Introduced

• Added lerp_smooth to Vec2, Vec3 and math
• Added lerp to Vec2

PR Checklist

• I have documented any user-visible changes to the code in the documentation folder
• I agree that the changes introduced in this PR are dual-licensed under the LGPL-3.0 and MIT licenses (Why?)
• I have added applicable tests, or at least not introduced any failures