Update exception in getStack for SDK v3

[SanariSan]

Issue #127

Description of changes:
Adjusted for SDK v3 compatibility
See API documentation, Throws section

For testing I've hardcoded my stack details and added console.log(e)
Error in catch block looks like this:

CloudFormationServiceException [ValidationError]: Stack with id test-prod-vpc does not exist
    at throwDefaultError (/home/user/Code/libs/aws-cloudformation-github-deploy/node_modules/@smithy/smithy-client/dist-cjs/default-error-handler.js:8:22)
    at /home/user/Code/libs/aws-cloudformation-github-deploy/node_modules/@smithy/smithy-client/dist-cjs/default-error-handler.js:18:39
    at de_DescribeStacksCommandError (/home/user/Code/libs/aws-cloudformation-github-deploy/node_modules/@aws-sdk/client-cloudformation/dist-cjs/protocols/Aws_query.js:1727:12)
    at processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async /home/user/Code/libs/aws-cloudformation-github-deploy/node_modules/@smithy/middleware-serde/dist-cjs/deserializerMiddleware.js:7:24
    at async /home/user/Code/libs/aws-cloudformation-github-deploy/node_modules/@aws-sdk/middleware-signing/dist-cjs/awsAuthMiddleware.js:30:20
    at async /home/user/Code/libs/aws-cloudformation-github-deploy/node_modules/@smithy/middleware-retry/dist-cjs/retryMiddleware.js:31:46
    at async /home/user/Code/libs/aws-cloudformation-github-deploy/node_modules/@aws-sdk/middleware-logger/dist-cjs/loggerMiddleware.js:7:26 {
  '$fault': 'client',
  '$metadata': {
    httpStatusCode: 400,
    requestId: '4995d2b8-****-****-****-30e1de77fc62',
    extendedRequestId: undefined,
    cfId: undefined,
    attempts: 1,
    totalRetryDelay: 0
  },
  Type: 'Sender',
  Code: 'ValidationError'
}

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[kddejong]

While the exception does exist in v3 it isn't returned by the describe stacks command. Looks like that this error is only returned by a small set of commands... Thanks for submitting this.