_base/lang.rst needs some proof reading

[ChristianHeinrich]

I just looked through lang.rst and I need to admit that there are quite a few mistakes (grammatically) in there. Unfortunately, since I don't know a lot about dojo, these issues aren't easy for me to fix.

For instance, extends() contains the following sentence:

The way the dojo/parser works, a custom attribute on the node will be recognized, as in the interest of performance, only declared members are mixed as part of the parsing process.

I'm actually not even sure what the author's intention is.

The next section ("Extending dijit/_WidgetBase") contains the sentence

A potentially confusing result of the above actually provides us a lot of flexibility.

I already opened a PR on GitHub? for some issues, but I guess this page might require more work.

[bill]

I agree, that section on the parser makes no sense.

[dylan]

I've attempted to clean-up the remaining issue at ​https://github.com/dojo/docs/commit/7eb093c090bbf0f1e1550268f1a0d94ed189a59b

If I had more time, I'd probably rewrite the entire file, but I focused on the issue reported beyond the original pull request.