(vendor): Add openvr, imgui, implot, glfw

Also update imgui implot and glfw.

.gitmodules

@@ -1,3 +1,15 @@
 [submodule "lib/minhook"]
 	path = lib/minhook
 	url = https://github.com/bdunderscore/minhook.git
+[submodule "lib/openvr"]
+	path = lib/openvr
+	url = https://github.com/ValveSoftware/openvr
+[submodule "lib/imgui"]
+	path = lib/imgui
+	url = https://github.com/ocornut/imgui
+[submodule "lib/implot"]
+	path = lib/implot
+	url = https://github.com/epezent/implot.git
+[submodule "lib/glfw"]
+	path = lib/glfw
+	url = https://github.com/glfw/glfw