fix markInputRules for italics mark

add another layer of matching by introducing support for second match group
since javascript (at least in current browsers) still lacks lookbehind in regex

so now supports

/nomatch(markstart(text)markend)nomatch/ and still supports the
/markstart(text)markend/ syntax

all `nomatch` will be kept as is so kindof simulating lookbehinds

packages/tiptap-commands/src/commands/markInputRule.js

@@ -3,23 +3,28 @@ import { InputRule } from 'prosemirror-inputrules'
 export default function (regexp, markType, getAttrs) {
   return new InputRule(regexp, (state, match, start, end) => {
     const attrs = getAttrs instanceof Function ? getAttrs(match) : getAttrs
-        const { tr } = state
-        let markEnd = end
+    const { tr } = state
+    const m = match.length - 1
+    let markEnd = end
+    let markStart = start
 
-    if (match[1]) {
-      const startSpaces = match[0].search(/\S/)
-      const textStart = start + match[0].indexOf(match[1])
-      const textEnd = textStart + match[1].length
-      if (textEnd < end) {
-        tr.delete(textEnd, end)
+    if (match[m]) {
+      const matchStart = start + match[0].indexOf(match[m - 1])
+      const matchEnd = matchStart + match[m - 1].length - 1
+      const textStart = matchStart + match[m - 1].lastIndexOf(match[m])
+      const textEnd = textStart + match[m].length
+
+      if (textEnd < matchEnd) {
+        tr.delete(textEnd, matchEnd)
       }
-      if (textStart > start) {
-        tr.delete(start + startSpaces, textStart)
+      if (textStart > matchStart) {
+        tr.delete(matchStart, textStart)
       }
-      markEnd = start + startSpaces + match[1].length
+      markStart = matchStart
+      markEnd = markStart + match[m].length
     }
 
-    tr.addMark(start, markEnd, markType.create(attrs))
+    tr.addMark(markStart, markEnd, markType.create(attrs))
     tr.removeStoredMark(markType) // Do not continue with mark.
     return tr
   })

packages/tiptap-extensions/src/marks/Italic.js

@@ -30,7 +30,8 @@ export default class Italic extends Mark {
 
   inputRules({ type }) {
     return [
-      markInputRule(/(?:^|[^*_])(?:\*|_)([^*_]+)(?:\*|_)$/, type),
+      markInputRule(/(?:^|[^_])(_([^_]+)_)$/, type),
+      markInputRule(/(?:^|[^*])(\*([^*]+)\*)$/, type),
     ]
   }