Fix functionality, add readme

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Author: ChristophWurst

README.md

@@ -0,0 +1,35 @@
+# XML Lint Action
+
+This action validates an xml files with a given xml schema using xmllint.
+
+## Inputs
+
+### `xml-file`
+
+**Required** The name of the source (.xml) file.
+
+### `xml-schema-file`
+
+**Required** The name of the schema (.xsd) file.
+
+## Example usage
+
+```yml
+name: Lint
+
+on: [push]
+
+jobs:
+  xml-linters:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@master
+    - name: Download schema
+      run: wget https://apps.nextcloud.com/schema/apps/info.xsd
+    - name: Lint info.xml
+      uses: ChristophWurst/xmllint-action@v1
+      with:
+        xml-file: ./appinfo/info.xml
+        xml-schema-file: ./info.xsd
+```

entrypoint.sh

@@ -1,3 +1,3 @@
 #!/bin/sh -l
 
-# xmllint $1 --schema $2 --noout
+xmllint $1 --schema $2 --noout