Add inverse trigonometric functions

[GlitchlessCode]

The Suggestion

Add the following functions:

• sin⁻¹(x)
• cos⁻¹(x)
• tan⁻¹(x)
• atan2(y, x)

  Implementation description

• All implementations except for gm:arctan2 use the sqrt function from #4
• gm:arcsin, gm:arccos and gm:arctan fail when $(x) is not present
  • gm:arcsin and gm:arccos both fail when $(x) is not with the bounds -1 ≤ x ≤ 1
• gm:arctan2(y, x) fails when either $(x) or $(y) are not present
  • Thanks to certain quirks of how minecraft works, gm:arctan2(y, x) is actually more efficient than gm:arctan
• Ensured same formatting and error checking to the original codebase
• Updated README to add gm:arcsin, gm:arccos, gm:arctan and gm:arctan2 to list of functions

[GlitchlessCode]

I just realised that I accidentally left a debugging tellraw in my code, but I fixed that now :P

[gibbsly]

epic