Fix issue #11282.
When a new perspective (layout) is created and we are in a Projectile
project, add all buffers belonging to that project to the perspective.
* layers/+spacemacs/spacemacs-layouts/funcs.el
(spacemacs//add-project-buffers-to-persp): Add new function.
* layers/+spacemacs/spacemacs-layouts/packages.el
(spacemacs-layouts/init-persp-mode): Add
spacemacs//add-project-buffers-to-persp to persp-created-functions.
9fcf8c898d