private void post(Runnable action) {
        if (mainThreadHandler == null) {
            mainThreadHandler = new Handler(Looper.getMainLooper());
        }

        mainThreadHandler.post(action);
    }
Post an action to be run later.
RecyclerView doesn't like being mutated during a scroll. We can't detect when a
scroll is actually happening, unfortunately, so the best we can do is post actions
from notify* methods to be run at a later date.

@param action action to run
android/modules/module_common/src/main/java/github/tornaco/android/thanos/widget/section/SectioningAdapter.java