ci: do not expect the source map to be stable

Apparently there is some sort of instability regarding the source maps.
In this developer's setup, a sequence 'AACA;AAIA;' was replaced by
'AACA,2BAGA;AACA;' relative to the CI setup.

The purpose of those mappings is to figure out from stacktraces where
the culprit lies in the actual original code _in Typescript_. It is
unclear where those differences come from, but then, they are not a
blocker at all for running this GitHub Action. So let's ignore them.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

.github/workflows/test.yml

@@ -21,7 +21,7 @@ jobs:
         shell: bash
         run: |
           # `ncc` produces output with mixed line endings
-          test -z "$(git diff -aw HEAD | tee diff.txt)" || {
+          test -z "$(git diff -aw HEAD -- ':(exclude)dist/index.js.map' | tee diff.txt)" || {
             echo 'Files changed after `npm run package`'
             cat diff.txt
             exit 1