Bump version number in README.md

[mipli]

Update README.md to use the new 0.13 version

Description

Updated the Cargo.toml example in the README.md to use the new 0.13 version

Motivation and Context

Make sure people get the newest version when they copy the example lines from the README.md file

How Has This Been Tested?

Ran the tests and they're all fine, and it's a simple documentation change so did not feel the need to do further testing.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[jbr]

Thanks!