docs: Run rstcheck on README.rst, too.

Let's run rstcheck on the README.rst file in addition to the
documentation sources. One motivation is to help catch issues on the
releases table before merging. We update this table with a script after
cutting new releases, and it has occasionally led to formatting issues
in the past.

Fixes: #13366
Signed-off-by: Quentin Monnet <quentin@isovalent.com>

Documentation/check-build.sh

@@ -114,7 +114,7 @@ run_linter() {
         --ignore-directives "tabs,openapi" \
         --ignore-roles "${CONF_PY_ROLES}" \
         --ignore-substitutions "${CONF_PY_SUBSTITUTIONS}" \
-       -r . 2>&1 | \
+       -r . ../README.rst 2>&1 | \
        grep -v 'CRITICAL:rstcheck_core.checker:An `AttributeError` error occured. This is most propably due to a code block directive (code/code-block/sourcecode) without a specified language.'
 }