Created by: rohit2sharma95
Since shallow merge is used to merge popperConfig passed by the user for popper's config, this overrides the modifiers property instead of merging the array.
So creating popperConfig a function and then passing the default configuration as an argument gives users the ability to use the default configuration and merge it with their configuration. Keeping the previous type object in the supported types since removing it would be a breaking change.
Ref: https://github.com/twbs/bootstrap/pull/32443#issuecomment-748806985
@XhmikosR Let me know if it is a good idea