Updated link for InversifyJS middleware docs

[ahtik]

Middleware link update

Description

InversifyJS middleware docs changed from https://github.com/inversify/InversifyJS#middleware to https://github.com/inversify/InversifyJS/blob/master/wiki/middleware.md

Additionally, "Demo app" link to https://github.com/inversify/inversify-code-samples/tree/master/inversify-binding-decorator no longer works, but I'm not sure if https://github.com/inversify/inversify-binding-decorators is a good replacement as it's not provided as a "demo app".

How Has This Been Tested

Doc change

Types of changes

• [x] Docs change / refactoring / dependency upgrade
• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• [x] My code follows the code style of this project.
• [x] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [x] All new and existing tests passed.