[feature][QoL] Implement Snippets/Saved JS Scripts to exec

**Version and OS**
v0.39.21.1 on linux/docker

**Is your feature request related to a problem? Please describe.**
Getting to the point where I need to keep referencing old projects to get custom JS scripts and would think it would be nice to have an area where I could just click to add saved snippets/scripts.

e.g. Scroll to bottom, Scroll to Element, Click element, Emulate Mouse Click on element (since sometimes .click() does not work) among others. Not to mention would be able to create a sharable repo of scripts for others to use.

**Describe the solution you'd like**
Be able to select "saved" scripts/snippets from a dropdown to auto add into the Execute JS before change detected.

**Describe the use-case and give concrete real-world examples**
This is more of a quality of life improvement, where we would be able to save JS snippets for future use instead of storing/writing them "offsite"

Would also be nice to have a "public" repo users could share snippets/scripts with others so help streamline tasks.

The request covers saved JavaScript snippets, a dropdown in the Execute JS workflow, and a possible public sharing repository. Start by mapping where Execute JS before change detected is handled and how its UI stores script input; done would require an agreed scope for saving, selecting, executing, and optionally sharing snippets.

Written by the indexing model from the issue text.