Escape markdown sequences (#2208)

* escape inline markdown character

* fix typo

* improve document around custom markdown plugin and add escape sequence utils

* recover inline escape sequences on edit

* remove escape sequences from plain text body

* use `s` for strike-through instead of del

* escape block markdown sequences

* fix remove escape sequence was not removing all slashes from plain text

* recover block sequences on edit

src/app/plugins/markdown/inline/parser.ts

@@ -0,0 +1,40 @@
+import {
+  BoldRule,
+  CodeRule,
+  EscapeRule,
+  ItalicRule1,
+  ItalicRule2,
+  LinkRule,
+  SpoilerRule,
+  StrikeRule,
+  UnderlineRule,
+} from './rules';
+import { runInlineRule, runInlineRules } from './runner';
+import { InlineMDParser } from './type';
+
+const LeveledRules = [
+  BoldRule,
+  ItalicRule1,
+  UnderlineRule,
+  ItalicRule2,
+  StrikeRule,
+  SpoilerRule,
+  LinkRule,
+  EscapeRule,
+];
+
+/**
+ * Parses inline markdown text into HTML using defined rules.
+ *
+ * @param text - The markdown text to be parsed.
+ * @returns The parsed HTML or the original text if no markdown was found.
+ */
+export const parseInlineMD: InlineMDParser = (text) => {
+  if (text === '') return text;
+  let result: string | undefined;
+  if (!result) result = runInlineRule(text, CodeRule, parseInlineMD);
+
+  if (!result) result = runInlineRules(text, LeveledRules, parseInlineMD);
+
+  return result ?? text;
+};