Updating contribution.md file

[rajatgupta24]

Hey @ankitm123,
We've discussed few changes for the contribution.md file:

• Adding the linting section(I think it should be before build step.)
• Also I was thinking to add something like, you can found all the jx related issues in jx repo, for searching use labels as filters.

Any other suggestions are welcomed

[osamamagdy]

Regarding the linting section, we should add the golangci-lint version is v1.42.1
Also, adding a section for loading all the packages and modules by running go mod tidy could be helpful (before linting and building sections)
And at the pull request section, to ask a reviewer to review your changes, type /cc @<gethub_username> in a comment in your PR