fix: allow nested brackets in markup.escape

src/textual/markup.py

@@ -155,7 +155,7 @@ class StyleTokenizer(TokenizerState):
 
 def escape(
     markup: str,
-    _escape: _EscapeSubMethod = re.compile(r"(\\*)(\[[a-z#/@][^[]*?])").sub,
+    _escape: _EscapeSubMethod = re.compile(r"(\\*)(\[[a-z#/@].*?])").sub,
 ) -> str:
     """Escapes text so that it won't be interpreted as markup.
 

tests/test_escape_fix.py

@@ -0,0 +1,9 @@
+
+from textual.markup import escape, to_content
+
+def test_escape_nested_brackets():
+    problematic_string = "[type=x, v={'a[0]'}]"
+    escaped = escape(problematic_string)
+    assert escaped == "\\[type=x, v={'a[0]'}]"
+    content = to_content(escaped)
+    assert str(content) == problematic_string