[Doc] In the README.md, developer guide link can not be accessed

[Lan-ce-lot]

What happened:

In the README.md, developer guide link can not be accessed
developer guide

./docs/developer-guide.md
https://github.com/openyurtio/openyurt/blob/master/docs/developer-guide.md

I found the developer-guide.md in a version before, but the current master branch does not have this file. Should I delete this link?

What you expected to happen:

How to reproduce it (as minimally and precisely as possible):

Anything else we need to know?:

Environment:

• OpenYurt version:
• Kubernetes version (use kubectl version):
• OS (e.g: cat /etc/os-release):
• Kernel (e.g. uname -a):
• Install tools:
• Others:

others

[rambohe-ch]

@Lan-ce-lot Thank you for raising issue. The developer guide tutorials are removed here: https://openyurt.io/docs/developer-manuals/how-to-contribute