Add a map and filter seed_type

[jkomoros]

For doing a sub-seed while letting each value in the map.

It would be possible to do this entirely in userland if there were + and other arithmetic

• push
• spread (takes a and b, a and b can be objects or arrays (but must match). a or b can also be a non-array item, which will be automatically wrapped in arrays)
• index (takes a container and a search. Container can be a string, an array, or an object)
• Add a fromEnd bool to index
• an includes, starts_with, and ends_with function
• a slice() which can work on an array or string