This is absolutely fantastic work. One of the things I missed the most when upgrading to Quantum was losing the old Context Search extension by Ben Basson. Since then I've been delighted to discover that several replacements are available, but I think this one is the best of all of them.
It's super-configurable and you can adjust just about all aspects of how the extension works. The options page is a little tricky to work out initially, but you only need to tweak the defaults if you don't want to get too bogged down in the details.
There are three ways you can perform a search:
a) The normal way, through a sub-menu on the context menu
b) Directly on the context menu without needing the open a sub-menu (by installing the separate "Selection Context Search - mini" extensions)
c) Using the pop-up icons for one-click searching without the context menu
You can control where the search page appears. I prefer it as a background tab next to the current tab.
What I love is that you can replace a number of other extensions with this one. There are extensions that offer to translate the current page for you, but here you can translate either the selected text or the current page. Likewise, there are extensions for performing reverse Google Image searches, but this extension does that too. Brilliant!