Hacker News Reader

Works in Chrome too.

I use the shortcut "rs" for https://www.google.com/search?q=%s+site:reddit.com for searching reddit, and the shortcut "r" to go directly to the subreddit: https://www.reddit.com/r/%s

How exactly did you do that?

Should be under Chrome Settings -> Search engine -> Manage search engines and site search -> Site search.

You can add your custom search with the %s placeholder, a shortcut to use in the address bar, and name.

Also available in Edge. I had to add Brave Search manually to set it as the default search.