Update JavaGithubTrending.md

Author: Snailclimb

docs/github-trending/JavaGithubTrending.md

@@ -3,3 +3,4 @@
 - [2019 年 2 月](https://github.com/Snailclimb/JavaGuide/blob/master/docs/github-trending/2019-2.md)
 - [2019 年 3 月](https://github.com/Snailclimb/JavaGuide/blob/master/docs/github-trending/2019-3.md)
 - [2019 年 4 月](https://github.com/Snailclimb/JavaGuide/blob/master/docs/github-trending/2019-4.md)
+- [2019 年 5 月](https://github.com/Snailclimb/JavaGuide/blob/master/docs/github-trending/2019-5.md)