docs: update license (gnolang#1200)

This PR contains an update to the Gno Network Public License, a fork of
the GNU Afferro General Public License with an additional clause
regarding "Strong Attribution".

Additionally, this PR does the following:

1. **Move the GNO (Network) Public License to the root directory.** \
Rationale: the current `LICENSE.md` files says that the directories are
covered by two different licenses; but doesn't cover licensing for
`examples` or any other files.
2. **Change all links from www.gnu.org to gno.land.**
3. **Remove references to the "Lesser" Public License,** as it simply
doesn't exist.
4. **Move tm2/LICENSE.md to tm2/LICENSE,** as it's formatted for plain
text.
5. **Format the license for Markdown,** on the model of the existing
Markdown version of the GNU GPL.

Review & approval by @jaekwon required.