Make the content of component editable

Worked it out:

Just had to make the type a link, and then include a text component. E.g.

        editor.DomComponents.addType('custom_button', {
            model: {
                defaults: {
                    removable: true,
                    draggable: true,
                    badgable: true,
                    stylable: true,
                    highlightable: false,
                    selectable: true,
                    copyable: false,
                    resizable: true,
                    editable: true,
                    hoverable: true,
                    attributes: {class: 'btn gjs-button'},
                    type: 'link',
                    traits: [{
                        type: 'text',
                        label: 'URL',
                        name: 'href'
                    }],
                    content: 'hello wolrd'
                },
                reRender() {
                    this.view.render();
                }
            },
            extend: 'link',
            isComponent: function (el) {

                if (el.tagName === 'custom_button')
                    return {type: 'custom_button'};
            }

        });


        // Calendar Widget
        editor.BlockManager.add('custom_button', {
            id: 'custom_button',
            label: 'Button',
            category: 'GUI',
            content: {
                type: 'custom_button'
            }
        });