docs: Documentation updates

docs/app-template/introduction.md

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+# App Template
+
+## Background
+
+Since Helm [library charts](https://helm.sh/docs/topics/library_charts/) cannot be
+installed directly I have created a companion chart for the [common library](../../common-library/introduction).
+
+## Usage
+
+In order to use this template chart, you would deploy it as you would any other Helm chart.
+By setting the desired values, the common library chart will render the desired resources.
+
+Be sure to check out the [common library docs](../../common-library/introduction)
+and its [`values.yaml`](https://github.com/bjw-s/helm-charts/tree/main/charts/library/common/values.yaml) for
+more information about the available configuration options.
+
+#### Example
+
+This is an example `values.yaml` file that would deploy the [echo-server](https://github.com/jmalloc/echo-server)
+application.
+
+```yaml
+image:
+  repository: docker.io/jmalloc/echo-server
+  tag: 0.3.3
+
+service:
+  main:
+    ports:
+      http:
+        port: 8080
+
+ingress:
+  main:
+    enabled: true
+    ingressClassName: "nginx"
+    hosts:
+      - host: &host "echo-server.${INGRESS_DOMAIN}"
+        paths:
+          - path: /
+    tls:
+      - hosts:
+          - *host
+
+resources:
+  requests:
+    cpu: 15m
+    memory: 64M
+  limits:
+    memory: 128M
+```
+
+## Source code
+
+The source code for the app template chart can be found
+[here](https://github.com/bjw-s/helm-charts/tree/main/charts/other/app-template).