update: add the ability to pin the version

[fauzxan]

Summary

I want to include the ability to pin the holistics version that I want to install.

The usage will be as follows:

# Install latest version
curl -fsSL https://raw.githubusercontent.com/holistics/holistics-cli/refs/heads/master/install.sh | bash

# Install specific version
curl -fsSL https://raw.githubusercontent.com/holistics/holistics-cli/refs/heads/master/install.sh | HOLISTICS_VERSION=v1.2.3 bash

# Or export the variable first
export HOLISTICS_VERSION=v1.2.3
curl -fsSL https://raw.githubusercontent.com/holistics/holistics-cli/refs/heads/master/install.sh | bash

Asana

(asana link here)

Lasting Changes (Technical)

(please list down: code changes/things that have wide-effect; new libraries/functions added that can be used by others; examples below)

• (Added class EmailValidator to validate email address' validity)
• (Added Tenant#is_trial? check)

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklists

Please check directly on the box once each of these are done

• Update CHANGELOG.md
• Frontend: use new design system (see yarn docs)
• Documentation (if necessary)
• Tests (integration test/unit test)
• User Acceptance Test (Product Feature Review)
• Code Review