Validate date header?

### Which service(blob, file, queue, table) does this issue concern?

blob

### Which version of the Azurite was used?

2020.04 Version 3.7.0

### Where do you get Azurite? (npm, DockerHub, NuGet, Visual Studio Code Extension)

DockerHub

### What problem was encountered?

Azurite does not validate the `Date` header.

### Steps to reproduce the issue?

Create a request with a `Date: BOGUS` header. The request will succeed.

### Have you found a mitigation/solution?

The Azure blob service requires `RFC-2822` formatted dates and will error if the date is not formatted appropriately. It would be ideal if Azurite did the same validation since it is often used for testing before moving to production.