DynamoDB matcher toContainItemWithValues not found error in spec

[meenar-se]

When we try to use the dynamodb toContainItemWithValues matcher in the spec file its throwing an error saying matcher not found.
Example:
expect(tableName).toContainItemWithValues({pk:'ATTACH#1234567', sk: 'ATTACH#1234567', filename: 'test.png'})
Error: Property toContainItemWithValues does not exist on type JestMatchers

[meenar-se]

@agwhi - Can you please review this #37. Have also added the fix for this issue in that PR.