emin is explaining how to set a CUSTOM EXTENSION. You don't need to do that.
On bridge version 74+
Just set the twitterdub yescaptcha API key and it will use the default code for solving captcha
TOOLS > BROWSER > CAPTCHA > YESCAPTCHA > API KEY
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WARNING
If you try and set your own extension to solve the captcha AND yes the twitterdub function you will have two extensions trying to solve the captcha and I imagine it will cause issues.
Either do it manually with an extension you place there OR use the TD functionality. NOT both.