Add .yardoc to generated plugin .gitignore

[jonathanhefner]

Although Rails uses RDoc, Yard is also a popular choice. If the Yard gem is installed, the yard doc command will generate documentation for a plugin without the need for a Rake task or other configuration. Doing so generates doc/ and .yardoc/ directories. The former is already in the generated .gitignore file. This commit adds the latter.

[rafaelfranca]

Thank you for the pull request but I don't think Rails should deal with project specific choices.

[jonathanhefner]

@rafaelfranca Because the yard command can also parse and generate documentation for RDoc comments, I think of it more as a developer choice than a project choice. (As an example, here is documentation for Array#to_sentence generated by yard.)

[rafaelfranca]

It is a project choice in the sense that you need to chose to install yard and run it. Yes, it is true that it works out-of-the-box, but it is also true that Rails doesn't install it, neither Ruby. If you are choosing to install and run yard, you also add it to your .gitignore.

[rafaelfranca]

If it is a developer choice it is even easier, it should be in the developers global gitignore, like the editor specific files.