Update tests to use workdir param (#11)

## what
* Use input `workdir` 

## why
* `workdir`  was not used actually

Author: goruha

.github/workflows/test-negative.yml

@@ -25,6 +25,7 @@ jobs:
       - uses: ./
         id: current
         with:
+          workdir: ./tests/fixtures/
           file: test/docker-compose.yml
           service: app
           command: test/test-failure.sh

.github/workflows/test-positive.yml

@@ -25,6 +25,7 @@ jobs:
       - uses: ./
         id: current
         with:
+          workdir: ./tests/fixtures/
           file: test/docker-compose.yml
           service: app
           command: test/test-success.sh

action.yml

@@ -55,17 +55,22 @@ runs:
 
     - name: Start stack
       shell: bash
-      run: docker-compose -f ${{ inputs.file }} up -d
+      run: |
+        cd ${{ inputs.workdir }}
+        docker-compose -f ${{ inputs.file }} up -d
 
     - name: Test
       shell: bash
       run: |
+        cd ${{ inputs.workdir }}
         DIR=$(pwd)
         docker-compose -f ${{ inputs.file }} run -v ${DIR}:/github_workspace -w /github_workspace --entrypoint ${{ inputs.entrypoint }} --rm ${{ inputs.service }} -- ${{ inputs.command }}
 
     - name: Stop stacks
       if: always()
       shell: bash
-      run: docker-compose -f ${{ inputs.file }} down
+      run: |
+        cd ${{ inputs.workdir }}
+        docker-compose -f ${{ inputs.file }} down