Improve readme

[mrclmr]

• Fix code block outside of list item
• Make commands copyable
• Remove duplications

[dolmen]

This removes the PEG file syntax section which is more important to discover the project than the Usage section.
😞

I also wanted to move the Development section to a separate HACKING.md, because all the bootstrap/test stuff is only for contributors and just confusing when discovering the project.

[mrclmr]

This removes the PEG file syntax section which is more important to discover the project than the Usage section. 😞

No need to be sad. I can return this. But a second link with different formatting will not be needed.

I also wanted to move the Development section to a separate HACKING.md, because all the bootstrap/test stuff is only for contributors and just confusing when discovering the project.

Calling it development.md is fine. HACKING is a workaround or something unsual. This is just development documentation.