It's useful to expose replace section functions
It's useful to expose replace section functions

In case of extending text input handlers, it would be useful for users not copy/paste `replaceWithListSection`/`replaceWithHeaderSection`. For example if I just want to add a new handler to convert section to `backquote`, I can easily import replaceWithHeaderSection from this file without implementing this function again. So I propose expose these two functions.
bustle/mobiledoc-kit,bustlelabs/mobiledoc-kit,YoranBrondsema/mobiledoc-kit,bustle/mobiledoc-kit,Hstry/mobiledoc-kit,YoranBrondsema/mobiledoc-kit,bustlelabs/content-kit-editor,Hstry/mobiledoc-kit,bustlelabs/mobiledoc-kit,bustle/mobiledoc-kit,bustle/mobiledoc-kit,bustlelabs/content-kit-editor,mixonic/content-kit-editor,bustlelabs/mobiledoc-kit,bustlelabs/content-kit-editor,YoranBrondsema/mobiledoc-kit,Hstry/mobiledoc-kit,mixonic/content-kit-editor,mixonic/content-kit-editor