A JavaScript keyboard extension to encode selected text in Drafts 4.

DraftsEncodeURI

var input = getSelectedText();
var output = "";
if (input) {
    output = encodeURIComponent(input);
    var range = getSelectedRange();
    setSelectedText (output);
    setSelectedRange (range[0], output.length);
} else {
    input = getText();
    output = encodeURIComponent(input);
    setText(output);
}