Have a single tab for import functionality of Schema and Policy

[prernaadev01]

Problem description

Currently, when we click on Import button, we get a pop up which have three options for import:

1. Import from File : Select .schema/.policy file from the local system
2. Import from IPFS : Enter IPFS timestamp of specific schema/policy
3. Import from Excel : Select respective excel file of schema/policy to be imported.

As the functionality performs same operation, it would be good to have single tab, which allows the above three importing types.

Requirements

1.Remove the three tabs and make one universal import pop up.
2. Should be able to select any type of file, which needs to be then parsed and read it internally to import it.
3. Should be able to return specific errors when Guardian will not be able to parse the file.
4. Should be able to import and preview the file.

Definition of done

1. Import pop up should be global to any type of file type.
2. Should be able to parse and preview the file type.
3. Should throw required errors, if any issue with the file.
4. Documentation should be updated with all the updated screenshots.

Acceptance criteria

1. Should be able to accept all types of files.
2. Documentation update.

[denischasovskikh]

https://www.figma.com/file/r4opkmPm3TPieVSXTb0pjK/Design-file-(Guardian)?type=design&node-id=1246%3A27028&mode=design&t=JNeKhipmVVYds6vi-1