Read the inline text, and decode the escapes and references CommonMark spells (#33)

src/markdown/backtick-runs.ts

@@ -1,3 +1,20 @@
+export function backtickRun(text: string, index: number): number {
+  let length = 0
+  while (text.charAt(index + length) === '`') length += 1
+  return length
+}
+
+// Where the run of exactly `opener` backticks closing a code span begins, `undefined` where none does.
+export function closingBacktickRun(text: string, from: number, opener: number): number | undefined {
+  let cursor = from
+  while (cursor < text.length) {
+    const run = backtickRun(text, cursor)
+    if (run === opener) return cursor
+    cursor += run === 0 ? 1 : run
+  }
+  return undefined
+}
+
 export function fencedCodeBlock(info: string, body: string): string {
   const fence = '`'.repeat(Math.max(3, longestBacktickRun(body) + 1))
   return body === '' ? `${fence}${info}\n${fence}` : `${fence}${info}\n${body}\n${fence}`