Document dotted notation and expand tests

[shadowspawn]

Minimist supports a dotted notation which is currently undocumented and largely untested (other than regression tests for the CVE problems introduced by the feature!).

% node index.js --foo.bar=3
{ _: [], flag: false, f: false, foo: { bar: 3 } }

Related yargs documentation:

• https://github.com/yargs/yargs/blob/main/docs/tricks.md#objects
• https://github.com/yargs/yargs-parser#dot-notation