Add output cache for `VaryByValue`

[64J0]

Description:

We currently have the following possible cache middlewares on Giraffe:

• publicResponseCaching: Varies by headers;
• privateResponseCaching: Varies by headers;
• noResponseCaching;
• responseCaching: Varies by headers and query parameters.

In order to improve the project, we must add a new middleware, that let the cache vary by some value on the route endpoint.

For example, suppose we have this endpoint:

GET >=> routef "/pessoas/%s" // ...

The value of %s will change from request to request, but it could be useful to keep the response cached for a while in some cases that the value is the same.

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I got this idea when studying this project: https://github.com/andr3marra/rinha-de-backend-2023-q3-csharp/blob/main/src/Program.cs#L85.