EQL: implement math functions: add, divide, module, multiply, subtract

[aleksmaus]

• add (number, number) -> number
• divide (number, number) -> number
• modulo (number, number) -> number
• multiply (number, number) -> number
• subtract (number, number) -> number

[elasticmachine]

Pinging @elastic/es-ql (:Query Languages/EQL)

[Shubhangi2901]

Hi @aleksmaus I would like to work on this issue.

[aleksmaus]

Hi @Shubhangi2901, thank you for your interest in contributing to Elasticsearch. I have already started working on this issue.
There are plenty of other interesting issues to tackle for this project though. To find one, please check the good first issue label for example:
https://github.com/elastic/elasticsearch/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22