Merge branch 'readme' into 'master'

Add readme

See merge request social.coop/tech/wiki.social.coop!4

README.md

+# wiki.social.coop
+
+## Overview
+
+- Our wiki is hosted at https://wiki.social.coop
+- The content for the wiki comes from the [social.coop/general
+  wiki](https://git.coop/social.coop/general/-/wikis/home) here on git.coop (in
+  order to be easily editable by all)
+- This repo uses the [metalsmith](https://github.com/segmentio/metalsmith)
+  static site generator to build the markdown into html
+
+## Content
+
+- wiki is a git repo under the hood (it gets cloned into src/)
+- wiki also holds some templates (like gitlab issue and email) **which aren't
+  visible through the gitlab wiki interface**, so you need to clone the repo to
+  edit them
+
+## Authenticated routes
+
+- to secure a page behind mastodon authentication you need a handler using
+  `ensureAuthenticated` and (if you want to load a page from the wiki after
+  authentication) calling `next()`
+- ensureAuthenticated basically redirects to social.coop through [the mastodon
+  oauth flow](https://docs.joinmastodon.org/spec/oauth/) requesting the minimum
+  permissions (read:accounts) and, if successful, saves the user's mastodon
+  username into a signed cookie (to avoid redirecting next time)
+
+## Deployment
+
+- the wiki is deployed by [our ansible
+  config](https://git.coop/social.coop/tech/ansible) like so: `ansible-playbook
+  server.playbook.yml --tags wiki --user $YOUR_SERVER_USERNAME`
+- the code grabs various values from a `config.js` file (see
+  [example-config.js](https://git.coop/social.coop/tech/wiki.social.coop/-/blob/master/example-config.js))
+  which exists in the ansible config as
+  [config.js.j2](https://git.coop/social.coop/tech/ansible/-/blob/master/roles/wiki.social.coop/templates/config.js.j2)
+- the secret values in config.js are templated in config.js.j2 and mapped in
+  [server.playbook.yaml](https://git.coop/social.coop/tech/ansible/-/blob/master/server.playbook.yml)
+  to secrets encypted in [our pass repo](https://git.coop/social.coop/tech/pass)