convert readme from markdown to adoc

[govardhnn]

This PR does the following:

• Port the README.md > README.adoc keeping the structure intact
• Remove notes.txt
• modify gitignore to ignore adoc html builds

[govardhnn]

This PR is from my yesterday's proposed change to convert README from markdown to asciidoc. I will create a separate PR to divide the README based on resource categories.

Also note that the earlier used technique to use anchor tags to direct to a new page does not work with markdown. For reference: Stack Overflow Thread on trying new tab anchors in markdown

I would like to make further minor suggestions to commit to the same PR:

1. do not populate gitignore with ~

   • use an alias in your computer for emacs/vim to remove backup files before staging files to git, do not add backupfile suffixes to a public repository gitignore
     like: alias rme='find . -name "*~" -exec rm -rf {} +; find . -name "*#" -exec rm -rf {} +;'

2. remove the date added column - remove the need to check for outdated content, its the role of the community to raise an issue and if possible - a PR to remove outdated content.

   3. arrange all resources in alphabetical order of either Author or the tutorial to prevent bias in ordering

[thong-phn]

Hi @govardhnn, while this feature is impressive, our current focus is solely on the content. We'll revisit this aspect at a later stage.