fix: accept both calculator.test.js and calculator.tests.js in Step 3 workflow (#33)

The Step 3 CI workflow hardcoded the test file path as
src/tests/calculator.tests.js, but users following standard Jest
conventions naturally create calculator.test.js (singular). This caused
the keyphrase checker to fail with 'File does not exist' even though all
tests passed.

Changes:
- Add a detect step that checks for either calculator.test.js or
  calculator.tests.js and outputs the path for downstream steps
- Update step docs (2-step.md, 3-step.md) to use the standard Jest
  naming convention (calculator.test.js)

Fixes #32

Co-authored-by: Marcel Lupo <marcel.lupo@avanade.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: 3 people

.github/steps/2-step.md

@@ -128,7 +128,7 @@ Use the `!` command in Copilot CLI to execute shell commands directly from your
    > Create comprehensive unit tests for all the calculator functions:
    > - Expand tests based on the following example:
    >   - @images/calc-basic-operations.png
-   > - Add these tests to a src/tests/calculator.tests.js file
+   > - Add these tests to a src/tests/calculator.test.js file
    > - Use a popular Node.js testing framework if one isn't installed
    > - addition, subtraction, multiplication, and division
    > - test edge cases like division by zero

.github/steps/3-step.md

@@ -112,7 +112,7 @@ As you add features, Copilot CLI can help you:
    > Add tests for the new calculator operations: 
    > - Expand tests based on the following example:
    >   - @images/calc-extended-operations.png
-   > - Add new tests for the new operations to the existing src/tests/calculator.tests.js file
+   > - Add new tests for the new operations to the existing src/tests/calculator.test.js file
    > - Use a popular Node.js testing framework if one isn't installed
    > - Make sure to include edge case tests like square root of negative numbers
    > - Make sure all tests run and pass

.github/workflows/3-step.yml

@@ -57,28 +57,40 @@ jobs:
           file: exercise-toolkit/markdown-templates/step-feedback/checking-work.md
           edit-mode: replace
 
-      - name: Check if calculator.tests.js has a modulo test
+      - name: Detect calculator test file
+        id: detect-test-file
+        run: |
+          if [ -f "src/tests/calculator.test.js" ]; then
+            echo "path=src/tests/calculator.test.js" >> "$GITHUB_OUTPUT"
+          elif [ -f "src/tests/calculator.tests.js" ]; then
+            echo "path=src/tests/calculator.tests.js" >> "$GITHUB_OUTPUT"
+          else
+            echo "::error::Expected src/tests/calculator.test.js or src/tests/calculator.tests.js but neither was found"
+            exit 1
+          fi
+
+      - name: Check if calculator test file has a modulo test
         id: check-modulo-test
         continue-on-error: true
         uses: skills/action-keyphrase-checker@v1
         with:
-          text-file: src/tests/calculator.tests.js
+          text-file: ${{ steps.detect-test-file.outputs.path }}
           keyphrase: modulo
 
-      - name: Check if calculator.tests.js has a power test
+      - name: Check if calculator test file has a power test
         id: check-power-test
         continue-on-error: true
         uses: skills/action-keyphrase-checker@v1
         with:
-          text-file: src/tests/calculator.tests.js
+          text-file: ${{ steps.detect-test-file.outputs.path }}
           keyphrase: power
 
-      - name: Check if calculator.tests.js has a 'square root' test
+      - name: Check if calculator test file has a 'square root' test
         id: check-sqrt-test
         continue-on-error: true
         uses: skills/action-keyphrase-checker@v1
         with:
-          text-file: src/tests/calculator.tests.js
+          text-file: ${{ steps.detect-test-file.outputs.path }}
           keyphrase: 'square'
 
       - name: Update comment - step results