StrProp.startsWithOneOf(...) would be very useful

[eeverman]

Is your feature request related to a problem? Please describe.
When you need to specify a url, it would be nice to explicitly allow it to start with "http://" or "https://".
Its possible to do that with a regex, but its a relatively common need. Similarly, to specify a set of possible input files of select types, it would be nice to specify file endings, e.g. .png, .jpg, .gif.

Describe the solution you'd like
Add validators that are exposed as methods like this:

• startsWithOneOf(String[])
• startsWithOneOfIgnoringCase(String[])
• endsWithOneOf(String[])
• endsWithOneOfIgnoringCase(String[])

Notes for Hacktoberfest

These are some relatively simple additions to some existing classes. The new validations would be added to the StringValidator. Each type of validation is a subclass of that class and is implemented as an interclass within it.

If you are unfamiliar with the project, please look over the AndHow Site to get a basic understanding of what AndHow is, in particular, how Properties are used.

For this task:

• Be sure to work from the main branch
• Add the described validators to the StringValidator class, following the naming conventions of that class.
• Add methods to build those classes to the StrProp.StrBuilder class. The methods added to this builder should match the names listed above, e.g. startsWithOneOf(String[])
• Add tests for the new code, following existing examples.