Sync SDL3 wiki -> header

(cherry picked from commit 5df3eac925af8491259032ed275c1ec3e0e8e80b)

include/SDL_filesystem.h

@@ -64,7 +64,7 @@ extern "C" {
  * directory of the application as it is uncommon to store resources outside
  * the executable. As such it is not a writable directory.
  *
- * The returned path is guaranteed to end with a path separator ('\' on
+ * The returned path is guaranteed to end with a path separator ('\\' on
  * Windows, '/' on most other platforms).
  *
  * The pointer returned is owned by the caller. Please call SDL_free() on the
@@ -120,7 +120,7 @@ extern DECLSPEC char *SDLCALL SDL_GetBasePath(void);
  * - ...only use letters, numbers, and spaces. Avoid punctuation like "Game
  *   Name 2: Bad Guy's Revenge!" ... "Game Name 2" is sufficient.
  *
- * The returned path is guaranteed to end with a path separator ('\' on
+ * The returned path is guaranteed to end with a path separator ('\\' on
  * Windows, '/' on most other platforms).
  *
  * The pointer returned is owned by the caller. Please call SDL_free() on the