Add Feeds target for Telephone

Thanks for providing a patch for this!

I'm not so sure about cutting off the string if it is too long. You would be throwing away user input without notification. Even worse: it may result into an incomplete telephone number (I also noticed that you reference the Unicode class, but you didn't "import" that class at the top of the file).

Would you like to add an unit test for this target as well?

@Anybody
Other tests for targets can be found in feeds/tests/src/Unit/Feeds/Target. Which of these would be the most similar? EmailTest perhaps?

1. +++ b/tests/src/Unit/Feeds/Target/TelephoneTest.php
   @@ -0,0 +1,77 @@
   + * @coversDefaultClass \Drupal\feeds\Feeds\Target\StringTarget
   ...
   +class StringTargetTest extends FeedsUnitTestCase {
   

   The name of the class is wrong, apparently resulting into the test being ignored by the testbot.

2. +++ b/tests/src/Unit/Feeds/Target/TelephoneTest.php
   @@ -0,0 +1,77 @@
   +    $method(0, values);
   ...
   +    $method(0, values);
   

   No dollar sign for variable 'values'.

In the attached patch I've rewritten the test with a data provider. As I think randomness should be avoided in tests (as they can cause random test failures), I left these parts of the tests out.

Referenced the right class in the test and a few coding standard fixes.

@Anybody
You bet! ;)

Committed #17.