Adding IsHelm helper function

[Manasa Chinta (manasachi)]

Description

• Adding IsHelm() helper function which returns true a directory/file contains a Chart.yaml file. Does not validate the Chart.yaml itself, just checks to see it exists.
• Moved IsKustomize() to preprocessing_helpers.go as well to reduce clutter in preprocessing/ preprocessing_test.go.
• Added a test folder which for a test case which should return false for a dir without Chart.yaml

Fixes # (issue)
Feature # (details)

Type of change

Please delete options that are not relevant.

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

How Has This Been Tested?

Added Unit tests

• Test A
• Test B

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules