Add Edit Existing Functions as a postgres til.

postgres/edit-existing-functions.md

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+# Edit Existing Functions
+
+In the `psql` console, use `\ef` with the name of a function to fetch and
+open the definition of the function. The function will be opened in your
+system `$EDITOR` in the form of the `create or replace function` query.
+
+Executing
+
+```sql
+> \ef now
+```
+
+will open the following in your default editor
+
+```sql
+CREATE OR REPLACE FUNCTION pg_catalog.now()¬
+ RETURNS timestamp with time zone¬
+ LANGUAGE internal¬
+ STABLE STRICT¬
+AS $function$now$function$¬
+```