Add stubs to practice exercises S to V

[PakkuDon]

pull request

Related to #2133

This PR adds stubs for practice exercises starting with letters S through to V.

The following exercises have been omitted from this PR as they already have stubs defined:

• saddle-points - (Matrix.java)
• say - (Say.java)
• scrabble-score - (Scrabble.java)
• secret-handshake - (HandshakeCalculator.java)
• sieve - (Sieve.java)
• space-age - (SpaceAge.java)
• sum-of-multiples - (SumOfMultiples.java)
• tree-building - Looks like it has a stub defined? (BuildTree.java)
• triangle - (Triangle.java)
• twelve-days - (TwelveDays.java)
• two-fer - (Twofer.java)
• variable-length-quantity - (VariableLengthQuantity.java)

The following two exercises have been skipped as they are marked as deprecated in config.json

• strain
• trinary

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