MAINTAINERS: add @jxu (#13481)

* MAINTAINERS: add @jxu

Closes #13451

* MAINTAINERS: move @jxu to current roles

MAINTAINERS.md

@@ -72,6 +72,8 @@ If you are an owner of the organization, you can see an automated list [here](ht
   [13 November 2023](https://github.com/tldr-pages/tldr/issues/11460) — [27 March 2024](https://github.com/tldr-pages/tldr/issues/12209), [30 March 2024](https://github.com/tldr-pages/tldr/pull/11622#issuecomment-2027932865) — present
 - **Debaudh Ghosh ([@debghs](https://github.com/debghs))**:
   [16 August 2024](https://github.com/tldr-pages/tldr/issues/13450) — present
+- **jxu ([@jxu](https://github.com/jxu))**:
+  [18 August 2024](https://github.com/tldr-pages/tldr/issues/13451) — present
 - Owen Voke ([@owenvoke](https://github.com/owenvoke))
   [11 January 2018](https://github.com/tldr-pages/tldr/issues/1885) — [26 August 2018](https://github.com/tldr-pages/tldr/issues/2258)
 - Marco Bonelli ([@mebeim](https://github.com/mebeim)):