Add mostly-unchanged Helm chart from k8s-at-home

- Add the chart from k8s-at-home with some modifications
- Add the Apache 2.0 license to the new charts/paperless-ngx
  subdirectory, the license under which the chart was distributed by
  k8s-at-home. I believe the chart will have to maintain this license.

- Update the maintainers section and contact information to point to
  Paperless-ngx.
- Regenerate the README (using helm-docs)

- Add a GitHub actions configuration to publish the chart using GitHub
  pages. This makes the GitHub Pages page rendered by this repository
  usable as a Helm repository, without affecting potential future uses
  of the Pages site.

These are in response to discussion #1790.

.github/workflows/release-chart.yml

@@ -0,0 +1,31 @@
+---
+name: Release Charts
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  release_chart:
+    name: "Release Chart"
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+
+      - name: Configure Git
+        run: |
+          git config user.name "$GITHUB_ACTOR"
+          git config user.email "$GITHUB_ACTOR@users.noreply.github.com"
+      - name: Install Helm
+        uses: azure/setup-helm@v3
+        with:
+          version: v3.10.0
+
+      - name: Run chart-releaser
+        uses: helm/chart-releaser-action@v1.4.1
+        env:
+          CR_TOKEN: "${{ secrets.GITHUB_TOKEN }}"