ci: Add Codecov coverage reporting

Author: TsekNet

.github/workflows/ci.yml

@@ -23,4 +23,9 @@ jobs:
         run: go vet ./...
 
       - name: Test
-        run: go test -v -race -count=1 ./...
+        run: go test -v -race -coverprofile=coverage.txt -covermode=atomic -count=1 ./...
+
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v5
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}

README.md

@@ -3,7 +3,7 @@
   <h1>fleet-plan</h1>
   <p><strong><code>terraform plan</code>, but for <a href="https://fleetdm.com/">Fleet</a>.</strong></p>
 
-  [![codecov](https://codecov.io/gh/TsekNet/fleet-plan/branch/main/graph/badge.svg?token=9E0V5QX6G1)](https://codecov.io/gh/TsekNet/fleet-plan)
+  [![codecov](https://codecov.io/gh/TsekNet/fleet-plan/branch/main/graph/badge.svg?token=b71fa5cb-b607-4c0f-9f55-76cfffe8a054)](https://codecov.io/gh/TsekNet/fleet-plan)
   [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
   [![GitHub Release](https://img.shields.io/github/v/release/TsekNet/fleet-plan)](https://github.com/TsekNet/fleet-plan/releases)
 </div>