More docs and some restructuring

[navidshaikh]

In what area(s)?

Classifications:
/kind proposal
/kind doc
/kind cleanup

Describe the feature:

We need to add more docs for flags / features we have now, also some restructuring.

The landing page https://github.com/knative/client#docs links:

• User guide
• Generated documentation

User guide links:

• Workflows (docs/workflows)
• Operations (docs/operations)
• Traffic Splitting (docs/traffic)

For Workflows:

• docs/workflow/README.md <-- landing page linked from user guide docs/README.md
• docs/workflow/basic.md <-- linked from docs/workflows/README.md
  (can add other workflows )

For Operations:

• docs/operations/README.md <-- landing page linked from user guide docs/README.md
• docs/operations/auto_scaling.md <-- linked from docs/operations/README.md
• docs/operations/labelling.md
• docs/operations/resources.md
• docs/operations/all_others.md

For Traffic Splitting:

• docs/traffic/README.md <-- landing page linked from user guide docs/README.md
  (can have examples created under docs/traffic for e.g. blue/green deployment)

[buildbricks]

/assign joaedwar

[navidshaikh]

Fixed by #421 , the sub-sequent work to fill in docs in operations folder tracked in #424.