feat(core): escape corner brackets during serialization (#17)

During sterilization, we need to escape the corner brackets, because later they can be parsed as HTML

src/core/markdown/Markdown.test.ts

@@ -82,7 +82,7 @@ const serializer = new MarkdownSerializer(
 const {doc, p, h1, h2, li, ul, ol, br, pre} = builder;
 const {em, strong, code} = builder;
 
-const {same, serialize} = createMarkupChecker({parser, serializer});
+const {same, parse, serialize} = createMarkupChecker({parser, serializer});
 
 describe('markdown', () => {
     it('parses a paragraph', () => same('hello!', doc(p('hello!')))); // TODO: move test to extensions?
@@ -151,7 +151,7 @@ describe('markdown', () => {
     it('parses a line break', () =>
         same('line one\\\nline two', doc(p('line one', br(), 'line two'))));
 
-    it('ignores HTML tags', () => same('Foo < img> bar', doc(p('Foo < img> bar'))));
+    it('ignores HTML tags', () => parse('Foo < img> bar', doc(p('Foo < img> bar'))));
 
     it("doesn't accidentally generate list markup", () => same('1\\. foo', doc(p('1. foo'))));
 

src/core/markdown/MarkdownSerializer.js

@@ -294,7 +294,7 @@ export class MarkdownSerializerState {
     // have special meaning only at the start of the line.
     esc(str, startOfLine) {
         // TODO: add a setting which characters need to be escaped
-        str = str.replace(/[`\^+*\\~\[\]\{\}\$]/g, '\\$&');
+        str = str.replace(/[`\^+*\\~\[\]\{\}<>\$]/g, '\\$&');
         if (startOfLine) str = str.replace(/^[:#\-*+>]/, '\\$&').replace(/^(\s*\d+)\./, '$1\\.');
         return str;
     }