replace trailing whitespace with blackslash in README.md

As an alternative to the markdown trailing whitespace as a line
break, we use a trailing blackslash as a markdown line break.

2012/endoh1/README.md

@@ -1,8 +1,8 @@
 # Most complex ASCII fluid - Honorable mention
 
-Yusuke Endoh  
-<mame@ruby-lang.org>  
-<https://github.com/mame/>  
+Yusuke Endoh\
+<mame@ruby-lang.org>\
+<https://github.com/mame/>\
 Mastodon: [@mame@ruby.social](https://ruby.social/@mame)
 
 ## To build: