URL-based manifest fetching (instead of on-disk only) (#57)

* URL-based manifest fetching (instead of on-disk only)

Co-authored-by: Marko Malenic <[email protected]>

* Add mention of the manifestPath URL functionality in the README.md

* Add support for alternative git-style urls, drop the is-url npm package and document accordingly (fixes https://github.com/cargo-lambda/cargo-lambda-cdk/pull/57/files#r1848931070)

* Commit yarn.lock too since it's in the repo... (not package-lock.json)

* Do not try to git clone if the directory exists already and has no changes from upstream

* feat: add option to specify branch and force cloning every time

* deps: re-update yarn.lock

* deps: add package manager field to package.json

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Co-authored-by: Marko Malenic <[email protected]>

Author: brainstorm