testing: develop and document basic acceptance tests

[nlfiedler]

The input chips widget is just complex enough that a documented checklist of tests is appropriate. For instance, when making significant changes, it would be ideal to test the example on various platforms, especially android, ios, and web. Also, entering different sorts of text, such as symbols and numbers, can sometimes surface bugs. Another case is to enter some text, backspace, and enter different text.

[nlfiedler]

Case: add two or more chips, remove the left-most chip, put focus in text field, press backspace -- last chip should be removed (see issue #11).