Interconnect the README.md files into a tree.

[kuzminrobin]

The top-level README.md here lacks the link to the specification folder. And the README.md in the specification folder lacks the link to v0.1 folder.

(from the top-level README.md it is unclear what to do in order to familiarize with the QIR Spec)

Consider changing

1. here the fragment

The QIR specification is an effort

to fragment

The QIR specification is an effort

2. here the fragment

This specification defines an

to

This specification defines an