chore: place datetime component docs in correct location

README.md

@@ -523,6 +523,20 @@ sections = {
 }
 ```
 
+#### datetime component options
+
+```lua
+sections = {
+  lualine_a = {
+    {
+      'datetime',
+      -- options: default, us, uk, iso, or your own format string ("%H:%M", etc..)
+      style = 'default'
+    }
+  }
+}
+```
+
 #### diagnostics component options
 
 ```lua
@@ -641,20 +655,6 @@ sections = {
 }
 ```
 
-#### datetime component options
-
-```lua
-sections = {
-  lualine_a = {
-    {
-      'datetime',
-      -- options: default, us, uk, iso, or your own format string ("%H:%M", etc..)
-      style = 'default'
-    }
-  }
-}
-```
-
 #### tabs component options
 
 ```lua