Website: Update build script to exclude folders with an underscore prefix & rename docs/Deploy/kubernetes/ (#17817)

Closes: #17582

Changes:
- Updated the `build-static-content` script to not generate HTML pages
for files in subfolders that are prefixed with an underscore
- Renamed the `docs/Deploy/kubernetes` folder »
`docs/Deploy/_kubernetes`
- Documented this new behavior on the communications page of the
handbook.
- Updated commands on the Deploy Fleet on Kubernetes page.

---------

Co-authored-by: Mike McNeil <mikermcneil@users.noreply.github.com>

docs/Deploy/_kubernetes/README.md

@@ -0,0 +1 @@
+This folder includes the best practice YAML files for [deploying Fleet on Kubernetes](https://fleetdm.com/docs/deploy/deploy-fleet-on-kubernetes). 

docs/Deploy/_kubernetes/fleet-deployment.yml

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+apiVersion: apps/v1
+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:v4.43.3
+          command: ["fleet", "serve"]
+          ports:
+            - containerPort: 8443
+          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-master:6379
+            - name: FLEET_REDIS_PASSWORD
+              valueFrom:
+                secretKeyRef:
+                  name: fleet-cache-redis
+                  key: redis-password
+            - name: FLEET_SERVER_ADDRESS
+              value: "0.0.0.0:8443"
+            - name: FLEET_SERVER_CERT
+              value: "/secrets/fleet-tls/tls.crt"
+            - name: FLEET_SERVER_KEY
+              value: "/secrets/fleet-tls/tls.key"

docs/Deploy/_kubernetes/fleet-migrations.yml

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+apiVersion: batch/v1
+kind: Job
+metadata:
+  name: fleet-prepare-db
+spec:
+  template:
+    metadata:
+      name: fleet-prepare-db
+    spec:
+      containers:
+        - name: fleet
+          image: fleetdm/fleet:v4.43.3
+          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/Deploy/_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: 8443
+      protocol: TCP
+    - name: proxy-http
+      port: 80
+      targetPort: 80
+      protocol: TCP
+  selector:
+    app: fleet-webserver