chore: add `parallel-hashmap` as third party project

.gitmodules

@@ -19,3 +19,6 @@
 [submodule "third_party/pybind11"]
 	path = third_party/pybind11
 	url = https://github.com/pybind/pybind11.git
+[submodule "third_party/parallel-hashmap"]
+	path = third_party/parallel-hashmap
+	url = https://github.com/greg7mdp/parallel-hashmap.git

third_party/ThirdParty.cmake

@@ -4,6 +4,9 @@ set(KLSK_THIRD_PARTY ${KLSK_ROOT_DIR}/third_party)
 set(ABSL_PROPAGATE_CXX_STD ON)
 add_subdirectory(${KLSK_THIRD_PARTY}/abseil-cpp EXCLUDE_FROM_ALL)
 
+# parallel hashmap
+add_subdirectory(${KLSK_THIRD_PARTY}/parallel-hashmap EXCLUDE_FROM_ALL)
+
 if (KLSK_ENABLE_BENCHMARK)
   # google benchmark framework
   set(BENCHMARK_ENABLE_TESTING OFF)

third_party/parallel-hashmap

@@ -0,0 +1 @@
+Subproject commit be87c4139ed827fa80920c89922369701dccd41f