add psalm files

Author: Alexandru Bucur

.github/workflows/psalm.yml

@@ -0,0 +1,19 @@
+name: Psalm
+
+# Controls when the action will run. 
+on: [push, pull_request]
+
+# A workflow run is made up of one or more jobs that can run sequentially or in parallel
+jobs:
+  # This workflow contains a single job called "build"
+  build:
+    # The type of runner that the job will run on
+    runs-on: ubuntu-latest
+
+    # Steps represent a sequence of tasks that will be executed as part of the job
+    steps:
+      # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
+      - uses: actions/checkout@v2
+
+      - name: Psalm – Static Analysis for PHP
+        uses: docker://vimeo/psalm-github-actions

psalm.xml

@@ -0,0 +1,15 @@
+<?xml version="1.0"?>
+<psalm
+    errorLevel="7"
+    resolveFromConfigFile="true"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xmlns="https://getpsalm.org/schema/config"
+    xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"
+>
+    <projectFiles>
+        <directory name="src" />
+        <ignoreFiles>
+            <directory name="vendor" />
+        </ignoreFiles>
+    </projectFiles>
+</psalm>