Added multiple style props to the button widget:
- Button styles
- The background colour can change with a hex code
- elevation (box-shadow & colour)
- There are button variant contained (solid button), outlined (only borders), text (text buttons)
- Button can have an end icon or start icon
* added option to multipart form data for file or text upload
* updated styles for the dynamic-text-field-with-dropdown styled component
* added cypress tests for multipart body type
* code refactor: moved constants to ApiEditorConstants.ts
* updated multipart dropdown styles
* minor bug fix
