Fix deleteCharAfter not working at start of textblock
Fix deleteCharAfter not working at start of textblock

salzhrani/prosemirror,ProseMirror/prosemirror-markdown,bengler/prosemirror,salzhrani/prosemirror,kiejo/prosemirror,mattberkowitz/prosemirror,adrianheine/prosemirror,tzuhsiulin/prosemirror,mattberkowitz/prosemirror,adrianheine/prosemirror,tecnogram888/prosemirror,bengler/prosemirror,jacwright/prosemirror,tgecho/prosemirror,salzhrani/prosemirror,jacwright/prosemirror,tzuhsiulin/prosemirror,tgecho/prosemirror,kiejo/prosemirror,adrianheine/prosemirror,tzuhsiulin/prosemirror,kiejo/prosemirror,tecnogram888/prosemirror