Update table package formats to link to open MRs

What does this MR do?

As per https://gitlab.slack.com/archives/C3MAZRM8W/p1602768968001100, this MR combines the supported formats and suggested contributions in the Packages docs to include clear links to docs and open contributions.

Now, there is one table with the GitLab version column having:

• A release
• a WIP link
• Accepting Merge Requests (linking to docs on how to contribute

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team