Read file in Helm helper chart

I'm trying to create a helper chart which serves file content to other charts. Basically, since I have pretty much the same logging.xml configuration for all my apps I would like to define it at one place and share between the app charts.

So far I've managed to create a template:

{{- define "helpers.logging.xml" -}}
    logback.xml: |-
        {{ .Files.Get "resources/logback.xml" }}
{{- end }}

File structure in the helper chart looks like this:

helpers
  |--templates
     |--_helpers.tpl
  |-resources
     |--logback.xml
  Chart.yaml

In the main chart I try to pass results of the template. But it only works if I have a resouses/logging.xml file in the app chart itself.

apiVersion: v1
kind: ConfigMap
metadata:
  name: logging.{{ .Release.Name }}
  namespace: {{ .Release.Namespace }}
data:
  {{ include "helpers.logging.xml" . }}

Can someone advise me what is wrong? It it actually possible to do such a thing with Helm?

So in the end I found a soluton which suits my needs. Instead of sourcing from resource file I created an extra helper with a single template like this:

{{- define "templates.logback.xml" -}}
    logback.xml: |-
        <?xml version="1.0" encoding="UTF-8"?>
        <configuration>
          <!-- default configuration goes here -->
          <!--  ...  -->

          <!-- include custom config -->
          <include file="logback-custom.xml"/>
        </configuration>
{{- end }}

In a chart I have a configMap configured like this:

apiVersion: v1
kind: ConfigMap
metadata:
  name: logging.{{ .Release.Name }}
  namespace: {{ .Release.Namespace }}
data:
  {{ include "templates.logback.xml" . }}
  logback-custom.xml: |
    <included>
      <!-- custom config -->
    </included>