fix inheritance of positional attributes (dx, dy) for nested tSpans (#…

…266)

* fix inheritance of positional attributes (dx, dy) for nested tSpans

 - add inheritance mechanism
 - extend nested-tspans test case

fix #215

* archive reference files in CI tests when tests fail

.github/workflows/continous-integration.yml

@@ -12,3 +12,9 @@ jobs:
         node-version: '16.x'
     - run: npm install
     - run: npm run test:ci
+    - name: Archive reference files
+      if: ${{ failure() }}
+      uses: actions/upload-artifact@v3
+      with:
+        name: references
+        path: test/specs/**/reference.pdf

README.md

@@ -113,6 +113,10 @@ If you're debugging and want to have visual feedback, you should switch the `deb
 This ensures that a new reference PDF will be created on every run. You might also want to disable some tests in
 the `test/common/tests` array.
 
+Some tests might fail on your local machine, because of differences in text measuring. If you're contributing to
+a pull request and need to update the reference files, download the respective artifact from the CI build job on
+GitHub and check it in in a subsequent commit.
+
 ## Dependencies
 
 - [jsPDF](https://github.com/MrRio/jsPDF)