tools,doc: fix format-md files list

Adds content of doc/contributing/maintaining to the list

Fixes: #55216
PR-URL: #61147
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Aviv Keller <me@aviv.sh>

Author: StefanStojanovic

vcbuild.bat

@@ -798,6 +798,11 @@ for /D %%D IN (doc\*) do (
   for %%F IN (%%D\*.md) do (
     set "lint_md_files="%%F" !lint_md_files!"
   )
+  for /D %%S IN (%%D\*) do (
+    for %%F IN (%%S\*.md) do (
+      set "lint_md_files="%%F" !lint_md_files!"
+    )
+  )
 )
 %node_exe% tools\lint-md\lint-md.mjs %lint_md_files%
 ENDLOCAL
@@ -813,6 +818,11 @@ for /D %%D IN (doc\*) do (
   for %%F IN (%%D\*.md) do (
     set "lint_md_files="%%F" !lint_md_files!"
   )
+  for /D %%S IN (%%D\*) do (
+    for %%F IN (%%S\*.md) do (
+      set "lint_md_files="%%F" !lint_md_files!"
+    )
+  )
 )
 %node_exe% tools\lint-md\lint-md.mjs --format %lint_md_files%
 ENDLOCAL