add TODO for how to reduce matrix libraries

7 jobs for plotler-new in 4 minutes and 31 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Build
passed #6554433
build

00:04:31

passed #6554438
build_android

00:00:45

passed #6554434
build_clang_libcpp

00:03:09

passed #6554437
build_clazy

00:02:42

passed #6554436
build_mingw64_fedora

00:02:45

passed #6554435
build_ubuntu_16_04

00:02:28

passed #6554432
clang_format

00:00:54