Add a plugin system

Investigate plugin systems of other libraries to create a design for supporting extended - potentially commercial - functionalities.

Stages of the workflow:
Get input -> Render Input -> Generate image -> Save Image -> Generate App Code -> Save App Code

## Requirements
* Any plugin can go between any of the stages of the workflow
* Output of a plugin should match with the input we expect on the next stage
* Preferable order of the plugins should not matter - can we use events/hooks for this?

## Examples
* Webpack - https://github.com/webpack/tapable
* Vite
- https://github.com/vite-pwa/vite-plugin-pwa/blob/main/src/plugins/build.ts
- https://vitejs.dev/guide/api-plugin.html