Create CONSTANTS and INTERFACES in uiweb

[HarshRajat]

Rationale: currently, constants are passed as strings and interfaces are not defined which leads to issues.

Learning from restapi, we need to create CONSTANTS that will house different constants, for example CONSTANTS.CHAT.CHATPREVIEWLIST.NAME for more intiutive understanding

Same with interfaces, each interface should have an 'I' prefixed and should also be available from INTERFACES. For example: INTERFACES.CHAT.CHATPREVIEWLIST.IChatPreviewProps, etc

• First step should be notion page to ensure all team members agree on it.