Support for parameter overrides in CFn templates

I see that template parameters are supported via an argument:
https://github.com/aws/aws-extensions-for-dotnet-cli/blob/1877efebcf77c05e795911317ca1d32931dbd372/src/Amazon.Lambda.Tools/Commands/DeployServerlessCommand.cs#L579

However it would be great if you were also able to refer to a file, similar to [the AWS CLI](https://awscli.amazonaws.com/v2/documentation/api/latest/reference/cloudformation/deploy/index.html).

e.g. something like:
```
dotnet lambda deploy-serverless --template-parameters file://parameters.my-stack-prod.json
```

which is similar to:
```
aws cloudformation deploy --template stack.yaml --stack-name my-stack --parameter-overrides file://parameters.my-stack-prod.json
```

Start in src/Amazon.Lambda.Tools/Commands/DeployServerlessCommand.cs around line 579, where template parameters are currently handled, and compare the AWS CloudFormation deploy parameter-overrides documentation linked in the issue. Done means deploy-serverless accepts the requested file:// parameter source and applies its overrides during deployment.

Written by the indexing model from the issue text.