Update html5ever requirement from 0.27.0 to 0.29.0

Updates the requirements on [html5ever](https://github.com/servo/html5ever) to permit the latest version.
- [Commits](https://github.com/servo/html5ever/commits)

---
updated-dependencies:
- dependency-name: html5ever
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Cargo.toml

@@ -35,7 +35,7 @@ default = ["jetscii"]
 tree-builder = ["html5ever", "markup5ever_rcdom"]
 
 [dependencies]
-html5ever = { version = "0.27.0", optional = true }
+html5ever = { version = "0.29.0", optional = true }
 markup5ever_rcdom = { version = "0.3.0", optional = true }
 
 jetscii = { version = "0.5.1", optional = true }