Add basic plotter for WebGL

There're still a bunch of TODOs. Will address those when we actually
have a need for this.

Change-Id: I137390d384967ffb618e0ecda37503e1e0df8301
diff --git a/third_party/eigen/BUILD b/third_party/eigen/BUILD
index 54c5cd1..f3036f2 100644
--- a/third_party/eigen/BUILD
+++ b/third_party/eigen/BUILD
@@ -20,7 +20,7 @@
     ) + ["unsupported/Eigen/MatrixFunctions"] + glob([
         "unsupported/Eigen/src/MatrixFunctions/*.h",
     ]),
-    compatible_with = mcu_cpus,
+    compatible_with = mcu_cpus + ["@//tools:web"],
     includes = ["."],
     visibility = ["//visibility:public"],
 )