Adds openapi 3.1.0 if/then/else json schema features + fixes exclusiveMax/Min bug#234

spacether merged 17 commits intomasteropenapi-json-schema-tools/openapi-json-schema-generator:masterfrom

feat_adds_ifopenapi-json-schema-tools/openapi-json-schema-generator:feat_adds_ifCopy head branch name to clipboard