doc: Update README with UUID usage examples

[omkar-foss]

• [*] Do only one thing
• [*] Non breaking API changes
• [*] Tested

What did this pull request do?

This PR updates README with UUID usage examples.

User Case Description

Usage examples pertaining to the newly added UUID datatype for users' reference.

[omkar-foss]

@jinzhu small PR to update README with UUID example usage, please review when you get some time. Thanks.