Generate valid variable names from theme names and fix comma in output formatting

[thierryc]

trafficstars

Description

Implemented a JavaScript regex to sanitize theme names for use as variable names:

• Replaces spaces, hyphens, plus signs, and other invalid characters with underscores.
• Ensures adherence to JavaScript variable naming conventions.

Addressed a missing comma in output formatting:

• Added a comma between the "output" and "formula" elements for clarity and consistency.

Motivation

Fix output

[thierryc]

Adobe CLA Signed!

[GarthDB]

Moved work to https://github.com/adobe/leonardo/pull/243