Add more operators

[dplassgit]

Examples:

• Spaceship: x <=> y result is <0 if x<y, 0 if x==y, >0 if x>y
• Null-coalescing: x ?? y results in x if it is non-null, otherwise results in y
• x?.field results in x.field if x is not-null, otherwise results in null
• ^x : indexes the xth element counting from the end of an array or string, e.g., "hello"[^1] is "o". Similar to python negative indexes

[dplassgit]

Copied from beef https://www.beeflang.org/docs/language-guide/operators/