add weights conversion script for MiT

[divyashreepathihalli]

TODO:

• add weights conversion script here - https://github.com/keras-team/keras-hub/tree/master/tools/checkpoint_conversion
• Verify output with real inputs
• provide a working colab demo

Example PR - #1855.

[DavidLandup0]

Closed with #1893