sql: Add default jump handlers for SQL layer

Recent versions of `dumb-jump` have support for jumping to definitions for generic SQL buffers, and
support in Spacemacs requires that we enable these in the `sql` layer.

CHANGELOG.develop

@@ -2170,6 +2170,7 @@ Other:
   package (thanks to David Chen)
 - Added a code formatter for sql-mode (thanks to Seong Yong-ju)
 - Added connection between =org-mode= and =SQL layer= (thanks to Magnus Therning)
+- Added default jump handlers for SQL layer (thanks to Alex Palaistras)
 **** Spell-checking
 - Added spell checking transient state (thanks to Francesc Elies Henar)
 - Update to flyspell-correct v0.5 (thanks to Boris Buliga)

layers/+lang/sql/config.el

@@ -9,6 +9,8 @@
 ;;
 ;;; License: GPLv3
 
+(spacemacs|define-jump-handlers sql-mode)
+
 (defvar sql-capitalize-keywords nil
   "Capitalize keywords in SQL mode.")