add TODO for how to reduce matrix libraries

7 jobs for plotler-new in 9 minutes and 1 second (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Build
passed #7083937
build

00:08:37

passed #7083942
build_android

00:00:49

passed #7083938
build_clang_libcpp

00:09:00

passed #7083941
build_clazy

00:05:26

passed #7083940
build_mingw64_fedora

00:03:47

passed #7083939
build_ubuntu_16_04

00:02:35

passed #7083936
clang_format

00:01:11