changes to contributing.md to include directions to installation

[kanand77]

Reference Issues/PRs

Making it simpler for new users to directly link to installation steps from the CONTRIBUTING.md file

What does this implement/fix? Explain your changes.

Adding in a few extra lines to the CONTRIBUTING.md documentation to help new users avoid some easy bugs that they may first encounter if they don't have the environment properly set up.

Does your contribution introduce a new dependency? If yes, which one?

No

What should a reviewer concentrate their feedback on?

Seeing if the edit is well positioned or should be changed

Any other comments?

None

PR checklist

For all contributions

• [x ] I've added myself to the list of contributors.
• Optionally, I've updated sktime's CODEOWNERS to receive notifications about future changes to these files.
• [ x] I've added unit tests and made sure they pass locally.
  • None needed

For new estimators -- not needed

• I've added the estimator to the online documentation.
• I've updated the existing example notebooks or provided a new one to showcase how my estimator works.

[mloning]

Thanks @kanand77 - seems like a code quality check didn't pass, let me know if you need help with those.

[afzal442]

Thanks @kanand77 for this PR. I also had it in my mind to have such changes. Hoping it gets fixed and merged.

[mloning]

Nicely done, thanks @kanand77, now merged!