Add termpastefilter option

Change to specify a character to be filtered as an option when pasting on
the terminal.

src/nvim/options.lua

@@ -2820,6 +2820,14 @@ return {
       varname='p_tgc',
       defaults={if_true={vi=false}}
     },
+    {
+      full_name='termpastefilter', abbreviation='tpf',
+      type='string', list='onecomma', scope={'global'},
+      deny_duplicates=true,
+      vim=true,
+      varname='p_tpf',
+      defaults={if_true={vi="", vim=""}}
+    },
     {
       full_name='terse',
       short_desc=N_("hides notification of search wrap"),