Added a function that tests a single-digit hour (which should be prefixed with both + and 0) in various formats.
Added a function that tests a single-digit hour (which should be prefixed with both + and 0) in various formats.

target/iso-8601-date-formatter,evadne/ISO8601DateFormatter,analog-analytics/iso-8601-parser-unparser,mirion/iso-8601-date-formatter,realestate-com-au/iso8601parser,target/iso-8601-date-formatter,mirion/iso-8601-date-formatter,nixme/iso-8601-parser-unparser,boredzo/iso-8601-date-formatter,realestate-com-au/iso8601parser,nixme/iso-8601-parser-unparser,orta/iso-8601-date-formatter,boredzo/iso-8601-date-formatter,orta/iso-8601-date-formatter,caffco/iso-8601-date-formatter,analog-analytics/iso-8601-parser-unparser,hyperoslo/HYP8601,hyperoslo/HYP8601,hyperoslo/HYP8601,orta/iso-8601-date-formatter,boredzo/iso-8601-date-formatter,orta/iso-8601-date-formatter,mirion/iso-8601-date-formatter,caffco/iso-8601-date-formatter,realestate-com-au/iso8601parser,target/iso-8601-date-formatter,hyperoslo/HYP8601,caffco/iso-8601-date-formatter,evadne/ISO8601DateFormatter