Adding upstream version 2.6.3.

Signed-off-by: Daniel Baumann <daniel@debian.org>

.github/actions/core-test/Dockerfile

@@ -0,0 +1,13 @@
+FROM golang:bullseye
+
+SHELL [ "/bin/bash", "-x", "-e", "-c" ]
+
+ARG DEBIAN_FRONTEND=noninteraactive
+RUN apt-get update -y && \
+    apt-get install -qy --no-install-recommends \
+        cmake \
+        git \
+        make && \
+    git config --system --add safe.directory '*'
+
+CMD [ "make", "test-core", "test-skipped" ]

.github/actions/core-test/action.yml

@@ -0,0 +1,5 @@
+name: Core test
+description: Run the editorconfig-core-test suite
+runs:
+  using: docker
+  image: Dockerfile