feat(defaults): map Y to y$ #13268

rationale:
- consistent with D and Y
- long recommended by Vim's own ":help Y"

close #13268
close #416
ref #6289

src/nvim/testdir/setup.vim

@@ -21,6 +21,7 @@ set undodir^=.
 set wildoptions=
 set startofline
 set sessionoptions+=options
+unmap Y
 
 " Prevent Nvim log from writing to stderr.
 let $NVIM_LOG_FILE = exists($NVIM_LOG_FILE) ? $NVIM_LOG_FILE : 'Xnvim.log'