Add shared docs

exercises/shared/.docs/help.md

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+# Help
+
+To get help if you're having trouble, you can use one of the following resources:
+
+- [DRefLanguage](https://dlang.org/spec/spec.html) contains the D language specification
+- [DReference](https://dlang.org/phobos/index.html) contains the D standard library documentation
+- [/r/dlang](https://www.reddit.com/r/dlang) is the D subreddit.
+- [StackOverflow](http://stackoverflow.com/questions/tagged/d) can be used to search for your problem and see if it has been answered already. You can also ask and answer questions.

exercises/shared/.docs/tests.md

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+# Tests
+
+You can run the tests by running the following command in the exercise's directory:
+
+```bash
+dub test
+```
+
+## Passing the Tests
+
+Get the first test compiling, linking and passing by following the [three
+rules of test-driven development](http://butunclebob.com/ArticleS.UncleBob.TheThreeRulesOfTdd).
+Create just enough structure by declaring namespaces, functions, classes,
+etc., to satisfy any compiler errors and get the test to fail. Then write
+just enough code to get the test to pass. Once you've done that,
+uncomment the next test by moving the following line past the next test.
+
+```D
+static if (all_tests_enabled)
+```
+
+This may result in compile errors as new constructs may be invoked that
+you haven't yet declared or defined. Again, fix the compile errors minimally
+to get a failing test, then change the code minimally to pass the test,
+refactor your implementation for readability and expressiveness and then
+go on to the next test.
+
+Try to use standard D facilities in preference to writing your own
+low-level algorithms or facilities by hand.