feat(SchedulerStatic): Add dynamic key-value pairs for form blocks

[DominicWrege]

This commit introduces a new feature to the 'SchedulerStatic' interface by adding an index signature. Now, the interface allows dynamic assignment of key-value pairs, where the keys are of type 'string', and the corresponding values are of type 'SchedulerFormBlock'.

Typescript definitions for creating custom lightbox controls.

see: https://docs.dhtmlx.com/scheduler/custom_lightbox_editor.html

[AlexKlimenkov]

Thank you! We've merged these changes into the dev repo. They will be reflected in this repository as soon as we publish v6.0.5 bugfix update.