Update READMEs

[ipopescu]

While working on #75 and talking with our developers, I see that we need to update a few more sections:

• ~the tutorials under the /docs folder need to be checked and refreshed~ see #1115 Update CEP18 Tutorials
• the README in the contract directory needs to be populated (see reference)
• the main readme needs to be updated

[ipopescu]

@RitaMAllenCA @adam ETA for this new card: 2-3 points.

Current documentation:

• README.md - main readme needs some updates
• cep18/README.md => empty; add details similar to the cep-78 contract (modalities, errors etc)
• client-js/README.md => add examples for additional entry points -- work with Ryo to add code for: init, increase_allowace, decrease_allowance, change_security, mint, burn
• docs folder with tutorials and CLI commands => all of these need to be tested and refreshed; there are a lot of old instructions and the developers did not check these files (they just did a copy and replace)
• It would be good to auto generate the docs like the JS SDK https://casper-ecosystem.github.io/casper-js-sdk/; open a card for this.
• add prerequisites in the docs/ files; ex: install the Casper Client

Feedback from the developers on May 31:

• Turn on the eventing with an option; turn on minting with minting.
• We have changed the library to a contract, so we need to update the way we pull in the tests in the tutorial: https://github.com/casper-ecosystem/cep18/blob/master/docs/TUTORIAL.md. Ex the test fixture is not available anymore (pub struct TestFixture) => use TestContext instead
  • https://github.com/casper-ecosystem/cep18/blob/master/docs/TUTORIAL.md?plain=1#L104
  • any references to the library should be updated