[Docs] Adding all the markdown source files for docs.delta.io

[tdas]

Which Delta project/connector is this regarding?

• [ ] Spark
• [ ] Standalone
• [ ] Flink
• [ ] Kernel
• [x] Other (fill in here) - Docs

Description

This PR adds all the source files for generating the docs.delta.io

How was this patch tested?

Currently manually tested by python docs/generate_docs.py --livehtml

[scottsand-db]

Is there any prerequisite to getting this script to work?

➜  ~/delta git:(docs) python docs/generate_docs.py --livehtml
Building content
/bin/sh: sphinx-autobuild: command not found
Traceback (most recent call last):
  File "docs/generate_docs.py", line 112, in <module>
    main()
  File "docs/generate_docs.py", line 46, in main
    run_cmd(build_docs_args, env=env, shell=True, stream_output=True)
  File "docs/generate_docs.py", line 93, in run_cmd
    raise Exception("Non-zero exitcode: %s" % exit_code)
Exception: Non-zero exitcode: 127

[vkorukanti]

Instructions in docs/README.md work. Just need to setup the conda environment by following the instructions in docs/README.md and then the command python docs/generate_docs.py --livehtml generates the docs locally.