lsp layer must depend on yasnippet

- if this line is missing yasnippets might not be loaded because lsp-mode might
load the snippets before the auto-completion layer kick in.

CHANGELOG.develop

@@ -2024,6 +2024,7 @@ Other:
 - Fixed a delay when declaring prefixes for mode (thanks to Thanh Vuong)
 - Required =helm= or =treemacs= to download =helm-lsp= or =lsp-treemacs=
   (thanks to Steven Allen)
+- Required =yasnippet= (thanks to Ivan Yonchovski)
 **** Debug Adapter Protocol (DAP)
 - Layer variables:
   - Added variable =dap-enable-mouse-support=

layers/+tools/lsp/packages.el

@@ -11,7 +11,7 @@
 
 (defconst lsp-packages
   '(
-    lsp-mode
+    (lsp-mode :requires yasnippet)
     lsp-ui
     (company-lsp :requires company)
     (helm-lsp :requires helm)