You don't need a plugin.

OP's website basically creates queries of the form https://www.youtube.com/results?search_query=<search terms>

You can essentially do the same thing in Chrome and Firefox using a customized search.

Firefox

Go to YouTube and search for -reacts. This will generate a query like above (i.e. https://www.youtube.com/results?search_query=-reacts. Then create a bookmark for this link. Now, go to Bookmarks > Manage Bookmarks and click on the bookmark you just created. You can also go to Manage Bookmarks and manually create a bookmark from scratch. Either way, do the following.

Go to the URL and change it to https://www.youtube.com/results?search_query=%s-reacts.

Next, go to the Keyword field and add a shortcut. You can call it anything you want. For example you can enter yt.

To use the bookmark, just go the brower's address bar and type yt, then space and any search terms. The browser will replace the %s in the bookmark with your search terms, then go to the resulting URL.

Reference: Firefox: How to use keywords with bookmarks

Chrome

Go to Chrome's settings and click on Search Engine. Scroll to Site Search. Click on Add.

Enter any descriptive text in Search Engine (e.g. YouTube no reacts). In Shortcut, enter yt or whatever keyword you want. In URL, enter https://www.youtube.com/results?search_query=%s-reacts.

The click Add to save it.

Use it in the same way as Firefox.

Reference: Chrome: Add, edit, or remove site search shortcuts