Reorganize Fleet documentation (#12871)

Closes: #12611

Changes:
- Added three new documentation sections `/docs/get-started/`,
`/docs/configuration` and `/docs/rest api/`
- Updated folder names: `/docs/Using-Fleet/` » `/docs/Using Fleet` and
`/docs/deploying` » `/docs/deploy/`
- Moved `/docs/using-fleet/process-events.md` to `/articles` and updated
the meta tags to change it into a guide.
- Added support for a new meta tag: `navSection`. This meta tag is used
to organize pages in the sidebar navigation on fleetdm.com/docs
- Moved `docs/using-fleet/application-security.md` and
`docs/using-fleet/security-audits.md` to the security handbook.
- Moved `docs/deploying/load-testing.md` and
`docs/deploying/debugging.md` to the engineering handbook.
- Moved the following files/folders:
- `docs/using-fleet/configuration-files/` »
`docs/configuration/configuration-files/`
- `docs/deploying/configuration.md` »
`docs/configuration/fleet-server-configuration.md`
    -  `docs/using-fleet/rest-api.md` » `docs/rest-api/rest-api.md`
- `docs/using-fleet/monitoring-fleet.md` » `docs/deploy/rest-api.md`
- Updated filenames:
- `docs/using-fleet/permissions.md` »
`docs/using-fleet/manage-access.md`
- `docs/using-fleet/adding-hosts.md` »
`docs/using-fleet/enroll-hosts.md`
    -  `docs/using-fleet/teams.md` » `docs/using-fleet/segment-hosts.md`
- `docs/using-fleet/fleet-ctl-agent-updates.md` »
`docs/using-fleet/update-agents.md`
- `docs/using-fleet/chromeos.md` »
`docs/using-fleet/enroll-chromebooks.md`
- Updated the generated markdown in `server/fleet/gen_activity_doc.go`
and `server/service/osquery_utils/gen_queries_doc.go`
- Updated the navigation sidebar and mobile dropdown links on docs pages
to group pages by their `navSection` meta tag.
- Updated fleetdm.com/docs not to show pages in the `docs/contributing/`
folder in the sidebar navigation
- Added redirects for docs pages that have moved.

.

---------

Co-authored-by: Mike Thomas <mthomas@fleetdm.com>
Co-authored-by: Rachael Shaw <r@rachael.wtf>

docs/Configuration/README.md

@@ -0,0 +1,7 @@
+# Configuration
+
+### [Fleet server configuration](./fleet-server-configuration)
+Documentation for configuring the Fleet binary, managing osquery configurations, and running with systemd.
+
+### [Configuration files](./configuration-files/README.md)
+How to use configuration files and the fleetctl command line tool to configure Fleet.

docs/Configuration/configuration-files/kubernetes/fleet-deployment.yml

@@ -0,0 +1,51 @@
+apiVersion: apps/v1beta2
+kind: Deployment
+metadata:
+  name: fleet-webserver
+  labels:
+    app: fleet-webserver
+spec:
+  replicas: 2
+  selector:
+    matchLabels:
+      app: fleet-webserver
+  template:
+    metadata:
+      labels:
+        app: fleet-webserver
+    spec:
+      volumes:
+        - name: fleet-tls
+          secret:
+            secretName: fleet-tls
+      containers:
+        - name: fleet-webserver
+          image: fleetdm/fleet:4.0.1
+          command: ["fleet", "serve"]
+          ports:
+            - containerPort: 443
+          volumeMounts:
+            - name: fleet-tls
+              mountPath: "/secrets/fleet-tls"
+              readOnly: true
+          env:
+            - name: FLEET_MYSQL_ADDRESS
+              value: fleet-database-mysql:3306
+            - name: FLEET_MYSQL_PASSWORD
+              valueFrom:
+                secretKeyRef:
+                  name: fleet-database-mysql
+                  key: mysql-password
+            - name: FLEET_REDIS_ADDRESS
+              value: fleet-cache-redis:6379
+            - name: FLEET_REDIS_PASSWORD
+              valueFrom:
+                secretKeyRef:
+                  name: fleet-cache-redis
+                  key: redis-password
+            - name: FLEET_SERVER_ADDRESS
+              value: "0.0.0.0:443"
+            - name: FLEET_SERVER_CERT
+              value: "/secrets/fleet-tls/tls.crt"
+            - name: FLEET_SERVER_KEY
+              value: "/secrets/fleet-tls/tls.key"

docs/Configuration/configuration-files/kubernetes/fleet-migrations.yml

@@ -0,0 +1,23 @@
+apiVersion: batch/v1
+kind: Job
+metadata:
+  name: fleet-prepare-db
+spec:
+  template:
+    metadata:
+      name: fleet-prepare-db
+    spec:
+      containers:
+        - name: fleet
+          image: fleetdm/fleet:4.0.1
+          command: ["fleet", "prepare", "db"]
+          env:
+            - name: FLEET_MYSQL_ADDRESS
+              value: fleet-database-mysql:3306
+            - name: FLEET_MYSQL_PASSWORD
+              valueFrom:
+                secretKeyRef:
+                  name: fleet-database-mysql
+                  key: mysql-password
+      restartPolicy: Never
+  backoffLimit: 4

docs/Configuration/configuration-files/kubernetes/fleet-service.yml

@@ -0,0 +1,19 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: fleet-loadbalancer
+  labels:
+    app: fleet-loadbalancer
+spec:
+  type: LoadBalancer
+  ports:
+    - name: proxy-tls
+      port: 443
+      targetPort: 443
+      protocol: TCP
+    - name: proxy-http
+      port: 80
+      targetPort: 80
+      protocol: TCP
+  selector:
+    app: fleet-webserver