contributing: Add section for Eclipse Contributor Agreement

contributing/CONTRIBUTING.sh

@@ -100,6 +100,7 @@ log "Converting to markdown..."
 pandoc -s --toc --markdown-headings=atx --wrap=none -t gfm \
     --lua-filter="$SCRIPT_PATH/CONTRIBUTING.lua" \
     "$SCRIPT_PATH/../definitions.rst" \
+    "$SCRIPT_PATH/eca.rst" \
     "$SCRIPT_PATH/gitlab.rst" \
     "$SCRIPT_PATH/reuse.rst" \
     "$SCRIPT_PATH/dco.rst" \