Writing a plugin that triggers on a Control Panel Template Hook? I want to do something similar to this answer but for Craft 3 (eg. render some custom HTML in the Entry editing screen). I can't work out how to do this with the changed Craft 3 hooks. 

Should this be registered as an event now? What class/event ID should I be using to add code to cp.entries.edit.details?

(I'm new to Craft plugin dev so a little unclear how to proceed here)
Figured it out after browsing some existing plugins' source:

Craft::$app-&gt;getView()-&gt;hook('cp.entries.edit.details', function(array &amp;$context) {
    return '&lt;a href="#" class="btn"&gt;My Button!&lt;/a&gt;';
});