Add how-to for angular/twig integration (Continuation of #4159)

[SahAssar]

Continuation of bolt/bolt/issues/4159, Opening here instead since this is a a matter of adding the how-to to the docs and not anything actionable within bolt/bolt.

[GwendolenLynch]

Closing due to a lack of volunteers to document this, and it is corner case stuff better documented upstream.

Of course please feel free to unleash a drop bear on me if I am wrong, and we'll reopen … but someone will need to step up to do the docs as this has languished for 17 months now 😄