README: Fix list paragraphs

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1770>

README.md

@@ -46,7 +46,7 @@ with some additions:
 
  - Usage of g_autofree and g_autoptr are encouraged. The style used is
 
-```c
+    ```c
       g_autofree char *text = NULL;
       g_autoptr (MetaSomeThing) thing = NULL;
 
@@ -55,7 +55,7 @@ with some additions:
                             "text", text,
                             NULL);
       thinger_use_thing (rocket, thing);
-```
+    ```
 
  - Declare variables at the top of the block they are used, but avoid
    non-trivial logic among variable declarations. Non-trivial logic can be
@@ -65,14 +65,14 @@ with some additions:
  - Instead of boolean arguments in functions, prefer enums or flags when
    they're more expressive. The naming convention for flags is
 
-```c
-typedef _MetaSomeThingFlags
-{
+    ```c
+    typedef _MetaSomeThingFlags
+    {
       META_SOME_THING_FLAG_NONE = 0,
       META_SOME_THING_FLAG_ALTER_REALITY = 1 << 0,
       META_SOME_THING_FLAG_MANIPULATE_PERCEPTION = 1 << 1,
-} MetaSomeThingFlags;
-```
+    } MetaSomeThingFlags;
+    ```
 
  - Use `g_new0()` etc instead of `g_slice_new0()`.