Limit the depth for meson.build search

Searching the entire workspace can be be very costly, especially if the
workspace is on a network drive. This change makes the extension to
assume that meson.build is located either in the root of workspace, or
in any directory two levels down from the root.

Potentially fixes #234.

package.json

@@ -39,7 +39,9 @@
     "Programming Languages"
   ],
   "activationEvents": [
-    "workspaceContains:**/meson.build",
+    "workspaceContains:meson.build",
+    "workspaceContains:*/meson.build",
+    "workspaceContains:*/*/meson.build",
     "onDebugDynamicConfigurations",
     "onDebugDynamicConfigurations:cppdbg",
     "onDebugDynamicConfigurations:lldb"