chore(helm): bump chart version according to semver

[M0NsTeRRR]

Description

This is the first step for addressing Stirling-PDF issue #2107.

The new script will set both the application version (as before) and the chart version (new functionality) as follows:

• When the application major version is updated, the chart's major version is incremented (minor and patch will be set to 0).
• When the application minor version is updated, the chart's minor version is incremented (patch will be set to 0).
• When the application patch version is updated, the chart's patch version is incremented.

I’ve assumed that Stirling follows Semantic Versioning (SemVer) in the Gradle file.

Checklist

• I have read the Contribution Guidelines
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I have read the section Add New Translation Tags (for new translation tags only)