Add OSC 52 escape sequence yank

If the `tmux` `set-clipboard` option is set to `on` add the `osc52yank`
plugin and change `<leader>y` mapping to use it.

plugin/mappings.vim

@@ -76,11 +76,15 @@ nnoremap <leader>tm :tabmove<Space>
 " Clear search highlights
 nnoremap <leader><Space> :nohlsearch<CR>
 
-" System clipboard yank/put
-noremap <leader>y "+y
-noremap <leader>Y "+Y
-noremap <leader>p "+p
-noremap <leader>P "+P
+if g:use_osc52
+  noremap <leader>y :Oscyank<CR>
+else
+  " System clipboard yank/put
+  noremap <leader>y "+y
+  noremap <leader>Y "+Y
+  noremap <leader>p "+p
+  noremap <leader>P "+P
+endif
 
 " Quickly access spelling menu
 inoremap <C-s> <C-g>u<C-X>s

vimrc

@@ -199,3 +199,10 @@ Pack 'mustache/vim-mustache-handlebars'
 Pack 'joshglendenning/vim-caddyfile'
 Pack 'kbenzie/vim-khr'
 Pack 'jrozner/vim-antlr'
+
+" Plugins for remote integrations
+Pack 'greymd/oscyank.vim', {'type': 'opt'}
+let g:use_osc52 = trim(system('tmux show-options -g set-clipboard')) ==# 'set-clipboard on'
+if g:use_osc52
+  packadd oscyank.vim
+endif