doc: add organization header to README

This PR adds a slightly modified version of Organization README as the header for the project's README.

The rational behind this PR is that (IMO) the statement shown below should be in the forefront of the README, as it shows any wandering users what this project is

Node.js^® is a free, open-source, cross-platform JavaScript run-time environment—
that lets developers write command line tools and server-side scripts outside of a browser.

Additionally, for some users, it may be helpful to have quicklnks to some important pages (Issues, Downloads, Contributing)