Add Task.seq and Task.forEach

[lukewilliamboswell]

This was recently added to basic-cli in roc-lang/basic-cli#156

[lukewilliamboswell]

Posted in zulip

There is an issue in CI I haven't seen before -- it should be totally unrelated to the changes in that PR. The surgical linker is unhappy with __umodti3. I've had a quick look and haven't resolved yet, posting here in case anyone else is able to look at this further. I'll circle back later, but want to progress some other things rn.

thread 'main' panicked at 'Undefined Symbol in relocation, (+4ef2, Relocation { kind: PltRelative, encoding: Generic, size: +20, target: Symbol(SymbolIndex(+88)), addend: +fffffffffffffffc, implicit_addend: false }): Ok(Symbol { name: "__umodti3", address: +0, size: +0, kind: Unknown, section: Undefined, scope: Unknown, weak: false, flags: Elf { st_info: +10, st_other: +0 } })', crates/linker/src/elf.rs:1486:25

[RMailaender]

I think the description for seq doesn't fit.