Feature: Added Support For Vega-Lite Based Components

[Rupak182]

Related Issue
Fixes #517

Description of Changes
This PR adds support for Vega-Lite based Components .It uses vega-embed to generate a component based on the specs.

Type of Change

• 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)
• Documentation update
• New example
• Test improvement

Testing

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own 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 run my code against examples and ensured no errors
• Any dependent changes have been merged and published in downstream modules

Features

• Mosaic widget renders Vega-Lite-style JSON specs.
• Users can pass spec via Python and render rich charts.
• Compatible with browser and server execution.

[shivam-singhal]

@Rupak182 can you rebase and resolve conflicts?

[Rupak182]

@shivam-singhal Can you please check it out now?