contributing: Add section for Eclipse Contributor Agreement

Signed-off-by: Andrei Gherzan <andrei.gherzan@huawei.com>

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" \

contributing/eca.rst

+.. SPDX-FileCopyrightText: Huawei Inc.
+..
+.. SPDX-License-Identifier: CC-BY-4.0
+
+.. include:: ../definitions.rst
+
+Eclipse Contributor Agreement
+#############################
+
+Before your contribution can be accepted by the project team, contributors must
+electronically sign the [Eclipse Contributor Agreement
+(ECA)](http://www.eclipse.org/legal/ECA.php)
+
+Commits that are provided by non-committers must have a Signed-off-by field in
+the footer indicating that the author is aware of the terms by which the
+contribution has been provided to the project.  The non-committer must
+additionally have an Eclipse Foundation account and must have a signed Eclipse
+Contributor Agreement (ECA) on file.
+
+For more information, please see the [Eclipse Committer Handbook](https://www.eclipse.org/projects/handbook/#resources-commit)