* Fix WASM bullet/code indentation

* Use `console` code highlighting where appropriate

… which handles the prefix `$` correctly.

* Migrate feature proposal template to MarkDown

* Set language on code blocks

* More on tutorial

* More on tutorial

* More on tutorial

* More on tutorial: clearer example output

https://github.com/ruby/optparse/commit/84dfd92d2a

https://github.com/ruby/optparse/commit/f209276f79

https://github.com/ruby/optparse/commit/cccb28e0de

-   Added example in "Argument Converters"; it doesn't seem right for a tutorial to have no example in one of its topics (and instead just linking elsewhere).
-   Added section "Command-Line Abbreviations."
 -  Added section "Keyword Argument into," showing how to:
     -  Collect options.
     -  Check for missing options.
     -  Provide option defaults.

https://github.com/ruby/optparse/commit/39d39676c4

* Resolve shared mixed_names.rb

* Add long option with negation

* Show --help for all examples

* Table of contents for tutorial

* Move argument converters to separate rdoc

* Add references to argument_converters.rdoc

* Tune up argument converters

* Change explicit links to auto-links

https://github.com/ruby/optparse/commit/c91ed8d33d

https://github.com/ruby/optparse/commit/9a2352c1c9

* More on tutorial: clearer example output

https://github.com/ruby/optparse/commit/84dfd92d2a