Format all files with prettier VSCode plugin and add yamllint in CI (#413)

@justusbunsi to end my formatting mess... ;)

I am not fully sure myself about the linebreaks in `values.yaml` but I don't think there's an easy way to change that behavior.

Reviewed-on: https://gitea.com/gitea/helm-chart/pulls/413
Reviewed-by: justusbunsi <justusbunsi@noreply.gitea.io>
Co-authored-by: pat-s <patrick.schratz@gmail.com>
Co-committed-by: pat-s <patrick.schratz@gmail.com>

.yamllint

@@ -0,0 +1,20 @@
+---
+extends: default
+
+ignore: |
+  .yamllint
+  node_modules
+  templates
+
+
+rules:
+  truthy:
+    allowed-values: ['true', 'false']
+    check-keys: False
+    level: error
+  line-length: disable
+  document-start: disable
+  comments:
+    min-spaces-from-content: 1
+  braces:
+    max-spaces-inside: 2