Migrate to NestJS

[radhay-1199]

• Migrate to NestJs (Typescript)
• Define Types and Interfaces for APIs and Objects
• Set up modules for health checks and swagger
• Set up deploy scripts for local development
• Extend templater's services to make Doc Gen's Backend

[yuvrajsab]

Milestone 1:
We can start by implementing 2 APIs

1. Register template API - this API will use Templater service for creating new templates
2. Generate PDF API - this API will use puppeteer to create PDFs

Milestone 2:
We can focus on extending register template API by implementing Google docs feature that will take template in the form of google doc and convert that to HTML and pass that to templater for registering it.

Milestone 3:
We can focus on exporting output to different type of format i.e. docx. PDF, HTML, etc.