document how to add custom themes

README.md

@@ -566,6 +566,48 @@ gitea:
   podAnnotations: {}
 ```
 
+### Themes
+
+Custom themes can be added via k8s secrets and referencing them in `values.yaml`.
+
+```yaml
+extraVolumes:
+  - name: gitea-themes
+    secret:
+      secretName: gitea-themes
+
+extraVolumeMounts:
+  - name: gitea-themes
+    readOnly: true
+    mountPath: "/data/gitea/public/css"
+```
+
+The secret can be created via `terraform`:
+
+```hcl
+resource "kubernetes_secret" "gitea-themes" {
+  metadata {
+    name      = "gitea-themes"
+    namespace = "gitea"
+  }
+
+  data = {
+    "theme-custom.css"      = "${file("FULL-PATH-TO-CSS")}"
+    "theme-custom-dark.css" = "${file("FULL-PATH-TO-CSS")}"
+  }
+
+  type = "Opaque"
+
+  depends_on = [kubernetes_namespace.gitea]
+}
+```
+
+or natively via `kubectl`:
+
+```bash
+kubectl create secret generic gitea-themes --from-file={{FULL-PATH-TO-CSS}} --namespace gitea
+```
+
 ## Parameters
 
 ### Global