chore: use markdownlint to lint the docs (#26792)

* chore: use markdownlint to lint the docs

* chore: fix markdown lints

Co-authored-by: Cheng Zhao <zcbenz@gmail.com>

script/check-trailing-whitespace.py

@@ -1,71 +0,0 @@
-#!/usr/bin/env python
-
-from __future__ import print_function, unicode_literals
-import argparse
-import io
-import os
-import sys
-
-SOURCE_ROOT = os.path.abspath(os.path.dirname(os.path.dirname(__file__)))
-DOCS_DIR = os.path.join(SOURCE_ROOT, 'docs')
-
-def main():
-  os.chdir(SOURCE_ROOT)
-
-  args = parse_args()
-
-  filepaths = []
-  totalDirs = 0
-  try:
-    for root, dirs, files in os.walk(DOCS_DIR):
-      totalDirs += len(dirs)
-      for f in files:
-        if f.endswith('.md'):
-          filepaths.append(os.path.join(root, f))
-  except KeyboardInterrupt:
-    print('Keyboard interruption. Please try again.')
-    return
-
-  trailingWhiteSpaceFiles = 0
-  for path in filepaths:
-    trailingWhiteSpaceFiles += hasTrailingWhiteSpace(path, args.fix)
-
-  print('Parsed through ' + str(len(filepaths)) +
-        ' files within docs directory and its ' +
-        str(totalDirs) + ' subdirectories.')
-  print('Found ' + str(trailingWhiteSpaceFiles) +
-        ' files with trailing whitespace.')
-  return trailingWhiteSpaceFiles
-
-def hasTrailingWhiteSpace(filepath, fix):
-  try:
-    with io.open(filepath, 'r', encoding='utf-8') as f:
-      lines = f.read().splitlines()
-  except KeyboardInterrupt:
-    print('Keyboard interruption while parsing. Please try again.')
-    return
-
-  fixed_lines = []
-  for num, line in enumerate(lines):
-    fixed_lines.append(line.rstrip() + '\n')
-    if not fix and line != line.rstrip():
-      print("Trailing whitespace on line {} in file: {}".format(
-          num + 1, filepath))
-      return True
-  if fix:
-    with io.open(filepath, 'w', newline='\n', encoding='utf-8') as f:
-      print(fixed_lines)
-      f.writelines(fixed_lines)
-
-  return False
-
-def parse_args():
-  parser = argparse.ArgumentParser(
-                      description='Check for trailing whitespace in md files')
-  parser.add_argument('-f', '--fix',
-                      help='Automatically fix trailing whitespace issues',
-                      action='store_true')
-  return parser.parse_known_args()[0]
-
-if __name__ == '__main__':
-  sys.exit(main())