feat: create customSelectorUrl config option

[lhjt]

This new configuration option lets the user decide what URL to look out for once video uploading has been completed.

For my use case, I want the script to detect when a short has been uploaded, which doesn't currently work (the URL generated by youtube starts with https://youtube/shorts rather than https://youtu.be, meaning the processing fails if it cannot find the uploaded short)

This configuration option will allow the search selector to be set by the user in the Video object, like so:

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This change is 

[fawazahmed0]

Thanks for the PR

[pierreminiggio]

I opened an issue related to this MR. @lhjt would be apreciated if you could look into it to see if the MR I attached to my issue solves the same problem as you experienced but without the need for a config'.
#141