Add ReSharper code inspection (#10)

And cancel workflows in progress to avoid having multiple of the same
workflow running

.github/workflows/resharper.yml

@@ -0,0 +1,36 @@
+name: "ReSharper"
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+on:
+  push:
+    branches: [ "master" ]
+  pull_request:
+    branches: [ "master" ]
+
+jobs:
+  inspect-code:
+    name: Inspect code
+    runs-on: ubuntu-latest
+    permissions:
+      actions: read
+      contents: read
+      security-events: write
+
+    strategy:
+      fail-fast: false
+
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v3
+
+    - name: Restore dependencies and tools
+      run: dotnet restore
+
+    - name: ReSharper CLI InspectCode
+      uses: muno92/resharper_inspectcode@1.6.0
+      with:
+        solutionPath: ./Boyfriend-CSharp.sln
+        ignoreIssueType: InvertIf
+        solutionWideAnalysis: true