Add erf function

[TalGrbr]

Description

It would be nice to have erf function for NDArray in addition to the existing erfinv function.

Will this change the current api? How?
NDArray api will have another method

Who will benefit from this enhancement?
Someone who needs the erf method

References

• Wikipedia: https://en.wikipedia.org/wiki/Error_function
• existing erf inv: https://javadoc.io/doc/ai.djl/api/latest/ai/djl/ndarray/NDArray.html#erfinv()

[TalGrbr]

Added in: #2842