How do I create a link in the node template?
Node templates have url variable which you can use in your template in the following way:

&lt;a href="{{ url }}"&gt;{{ label }}&lt;/a&gt;


(See node.html.twig for an example.)

In general, you can use link function in twig template:

{{ link(item.title, item.url, { 'class':['foo', 'bar', 'baz']} ) }}


(See Functions - In Twig Templates for a short list of twig functions provided by Drupal. Also take a look at TwigExtension for their source.)