Add missing file 'user.svg'. Close #27.

[GenericBIM]

Add missing file:

The Sign In link needs a user icon next to it. We're going to use user.svg for this, which should already be in our project.

Important Note

user.svg was in the starter project for this chapter. You can download it from https://github.com/PacktPublishing/NET-5-and-React-17---Second-Edition/blob/master/chapter-03/start/frontend/src/user.svg if you didn't start this chapter with the start project.