Added vim syntax tag to code blocks missing it

README.md

@@ -32,12 +32,12 @@ As of this writing (2023-04-30), this has only been tested in Vim v9, but is als
     If you want to have other file types to use this plugin, you may add them to the `allowlist` above.
 
 1.  By default, this plugin tries to determine if the cursor is in an email address field ('From:', 'To:', 'Cc:', 'Bcc:', in English).  The matching is case-insensitive.  If you use another language, that names these fields differently, you can modify this in $MYVIMRC by adding the `g:muttgoobook_address_fields` global variable.  This is designed to be a Vim regular expression, replace `['from', 'to', 'b\?cc']` accordingly:
-    ```
+    ```vim
     let g:muttgoobook_address_fields = '^\s*\(from\|to\|b\?cc\):\s*'
     ```
     The above pattern is the default if this variable isn't specified.
 1.  Also, if your mutt aliases file is in a different path than _${HOME}/.mutt/aliases_, you can override it in $MYVIMRC with the global variable `g:mutt_aliases`:
-    ```
+    ```vim
     let g:mutt_aliases = '~/.mutt/aliases'
     ```
     Again, what appears above is the default if not set explicitly to something else.  Any double-quotes (`"`) and backslashes (`\`) in the mutt aliases file will be removed before pasting the results of the completion to the currently edited mail file.