Add ability for external party to submit questionnaire reply

Part 2 of https://github.com/Signalen/product-steering/issues/286. For part 1, see https://github.com/Amsterdam/signals-frontend/pull/2414.

Signalen

To do:

[ ] Fix unit test

Context

This PR adds a new form allowing an external party to see what actions they should take and reply when they are ready.

After an incident is forwarded to an external party, the external party receives an e-mail with a link to the Signalen application. A questionnaire is shown with an explanation (title, location of the incident, attachments of the incident) and a form (text area, image upload). The backend configures what questions are shown. Currently the form only supports plain text and image answers. Upon completion of the form, the answer is submitted and the backend locks the form.

Changes

Move AttachmentViewer to shared folder and change the attachment type
Add prop to MapDetail to prevent marker from being focused
Add new route to ExternalReplyContainer component
Move IncidentReplyContainer components to ReplyForm folder (Notice, FileInput, Questionnaire, TextArea)
Add ExternalReplyContainer component
Add ExplanationSection component
Add Location component
Add useExternalReplyQuestionnaire hook

Design

InVision designs can be found here

Testing this branch

Follow instructions of https://github.com/Amsterdam/signals-frontend/pull/2414 to forward an incident to an external party
In the Django admin, add the below email template for the key Send mail signal forwarded to external reaction received. This example corresponds to the design but any municipality can choose their own template
Click on the link in the e-mail to open the questionnaire

Geachte behandelaar,

Bedankt voor het invullen van het actieformulier. Uw informatie help ons bij het verwerken van de melding.

**U liet ons het volgende weten**
{{ reaction }}

**Gegevens van de melding**\
Nummer: {{ formatted_signal_id }}\
Gemeld op: {{ created_at|date:"j F y, h.m" }} uur\
Plaats: {{ address  }}

Met vriendelijke groet,\
{{ ORGANIZATION_NAME }}

Signalen / frontend