Add requirements to imageSpec

[pingsutw]

TL;DR

Add support passing requirements.txt to image spec.

Type

• Bug Fix
• Feature
• Plugin

Are all requirements met?

• Code completed
• Smoke tested
• Unit tests added
• Code documentation added
• Any pending items have an associated Issue

Complete description

Example

from flytekit import task, workflow, ImageSpec

new_flytekit = "git+https://github.com/flyteorg/flytekit@01f2d63221467face8d35ed0af5308bbb3e66eaa"
image = ImageSpec(registry="pingsutw", packages=["pandas", new_flytekit], apt_packages=["git"], requirements="requirement.txt")


@task(container_image=image)
def bar():
    print("hello")
    print("hello")


@workflow
def wf() -> str:
    bar()
    return "hi"


if __name__ == '__main__':
    wf()

Tracking Issue

NA

Follow-up issue

NA

[cosmicBboy]

is this ready to go @pingsutw ?