Enable BC test (#244)

Author: Tigrov

.github/workflows/bc.yml

@@ -0,0 +1,23 @@
+on:
+  pull_request:
+    paths:
+      - 'src/**'
+      - '.github/workflows/bc.yml'
+      - 'composer.json'
+  push:
+    branches: ['master']
+    paths:
+      - 'src/**'
+      - '.github/workflows/bc.yml'
+      - 'composer.json'
+
+name: backwards compatibility
+
+jobs:
+  roave_bc_check:
+    uses: yiisoft/actions/.github/workflows/bc.yml@master
+    with:
+      os: >-
+        ['ubuntu-latest']
+      php: >-
+        ['8.1']