Main: refactored entry point API, removed redundant functions

src/esImportTest.ts

src/handlers/linkClickScroll/unitTest.html

src/handlers/loadScroll/unitTest.html

src/index.ts

src/integrationTest.html

src/scrollers/scrollToElement.unitTest.html

src/scrollers/scrollToOffset.unitTest.html

src/scrollers/scrollToTarget.unitTest.html