update CONTRIBUTING.md link to directly redirect to the relevant README section

### What problem did you find?
So when we go through the [Contributing Guideline](https://docs.crossplane.io/contribute/) page we often see if we click on [CONTRIBUTING.md](https://github.com/crossplane/crossplane/blob/master/CONTRIBUTING.md) it tend to redirect us to `contributing/` which is not convenient for new contributors like me.

### Proposed Solution
To enhance user experience we can redirect users whenever they click on [CONTRIBUTING.md](https://github.com/crossplane/crossplane/blob/master/CONTRIBUTING.md) to the required [README](https://github.com/crossplane/crossplane/tree/master/contributing#readme) file. This change would eliminate unnecessary clicks, making it more convenient for users to find the information they need rather than going from Click the CONTRIBUTING.md -> then again clicking on to contributing/ -> and then landing to the required [README](https://github.com/crossplane/crossplane/tree/master/contributing#readme) file

we can improve the structured documentation by adding appropriate links to the required section.