refactor: switch from npm to pnpm

This commit also installs the terser-webpack-plugin, since it was
implicitly installed by npm but not by pnpm, and we need it.

Fixed: twpowertools:211
Change-Id: Ie1f07c8fb8d089d70f56c058dbd6b4a8c44eb3c4
diff --git a/Makefile b/Makefile
index 91086df..5383c36 100644
--- a/Makefile
+++ b/Makefile
@@ -12,7 +12,7 @@
 		protoc -I=. --js_out=import_style=commonjs_strict:. proto/*.proto)
 
 node_deps:
-	npm ci --no-save
+	pnpm install --frozen-lockfile
 
 clean_dist:
 	rm -rf dist