docs: Lint rst files for trailing whitespace.

docs/index.rst

@@ -45,7 +45,7 @@ Contents:
 .. toctree::
    :maxdepth: 3
 
-   overview/index 
+   overview/index
 
 .. _zulip-in-production:
 

docs/translating/index.rst

@@ -11,4 +11,4 @@ Translating Zulip
    german
    polish
    russian
-   spanish   
+   spanish

tools/lint

@@ -90,7 +90,7 @@ def run():
             print('If you really know what you are doing, use --force to run anyway.')
             sys.exit(1)
 
-    backend_file_types = ['py', 'sh', 'pp', 'json', 'md', 'txt', 'text', 'yaml']
+    backend_file_types = ['py', 'sh', 'pp', 'json', 'md', 'txt', 'text', 'yaml', 'rst']
     frontend_file_types = ['js', 'css', 'handlebars', 'html']
     file_types = backend_file_types + frontend_file_types
     if args.backend:

tools/linter_lib/custom_check.py

@@ -690,6 +690,11 @@ def build_custom_checkers(by_lang):
             if custom_check_file(fn, 'txt', txt_rules, color):
                 failed = True
 
+        color = next(colors)
+        for fn in by_lang['rst']:
+            if custom_check_file(fn, 'rst', txt_rules, color):
+                failed = True
+
         color = next(colors)
         for fn in by_lang['yaml']:
             if custom_check_file(fn, 'yaml', txt_rules, color):