added new installation method (install.sh)

[zackbradys]

Please check below, if the PR fulfills these requirements:

• The commit message follows the guidelines.
• Tests for the changes have been added (for bug fixes / features).
• Docs have been added / updated (for bug fixes / features).

What kind of change does this PR introduce?

• Added an installation script (install.sh) for linux/darwin
• Updated README to reflect new installation method

What is the current behavior?

• Users manually run the installation commands with variables for each platform and architecture.

What is the new behavior (if this is a feature change)?

• Users are able to run a single command to install on each platform and architecture.

Does this PR introduce a breaking change?

• Users are still able to use the previous install process, but are encouraged to use the new one (default).

Other information:

• Pending https://get.hauler.dev being redirected to https://raw.githubusercontent.com/rancherfederal/hauler/main/install.sh

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[zackbradys]

Related hauler-docs PR:

• https://github.com/rancherfederal/hauler-docs/pull/6

Test installation script with the code below:

# install latest release
curl -sfL https://raw.githubusercontent.com/zackbradys/hauler/main/install.sh | sh

# install specific release
curl -sfL https://raw.githubusercontent.com/zackbradys/hauler/main/install.sh | HAULER_VERSION=0.4.0 sh

---

[amartin120]

LGTM!

[zackbradys]

Hey @bgulla, are you able add a record for https://get.hauler.dev to redirect to https://raw.githubusercontent.com/rancherfederal/hauler/main/install.sh?