feat: Add helm chart for the app (#65)

deployments/helm/README.md

@@ -0,0 +1,35 @@
+# 3proxy
+
+Important note: Since the chart is released together with the app under the same version (i.e., the chart version
+matches the app version), its versioning is not compatible with semantic versioning (SemVer). I will do my best to
+avoid non-backward-compatible changes in the chart, but due to Murphy's Law, I cannot guarantee that they will
+never occur.
+
+Also, this chart does not include Ingress configuration. If you need it, please, create it manually.
+
+## Usage
+
+```shell
+helm repo add proxy-3proxy https://tarampampam.github.io/3proxy-docker/helm-charts
+helm repo update
+
+helm install my-3proxy proxy-3proxy/proxy-3proxy --version <version_here>
+```
+
+Alternatively, add the following lines to your `Chart.yaml`:
+
+```yaml
+dependencies:
+  - name: proxy-3proxy
+    version: <version_here>
+    repository: https://tarampampam.github.io/3proxy-docker/helm-charts
+```
+
+And override the default values in your `values.yaml`:
+
+```yaml
+proxy-3proxy:
+  # ...
+  service: {ports: {http: 3128}}
+  # ...
+```