labeler: add ble mesh label

The ble mesh team created PR bot that gathers PRs from different
repos to report them in MS Team channel to follow up review state.
To operate well PR Bot needs label. This PR assignes `ble mesh` label.

Signed-off-by: Aleksandr Khromykh <aleksandr.khromykh@nordicsemi.no>

Author: alxelax

.github/labeler.yml

@@ -16,3 +16,10 @@
 
 "changelog-entry-required":
   - all: ["!doc/nrf/releases/release-notes-changelog.rst"]
+
+"ble mesh":
+  - "subsys/bluetooth/mesh/*"
+  - "include/bluetooth/mesh/*"
+  - "samples/bluetooth/mesh/*"
+  - "doc/nrf/libraries/bluetooth_services/mesh/*"
+  - "doc/nrf/ug_bt_mesh*"