vim-patch:9.1.1065: no digraph for "Approaches the limit" (#32289)

Problem:  no digraph for "Approaches the limit"
Solution: Add the digraph using .= (Hans Ginzel)

Add digraph Approaches the Limit

≐ U+2250 https://www.fileformat.info/info/unicode/char/2250/index.htm

closes: vim/vim#16508

3a621188ee

Co-authored-by: Hans Ginzel <hans@matfyz.cz>

src/nvim/digraph.c

@@ -1023,6 +1023,7 @@ static digr_T digraphdefault[] =
   { '?', '=', 0x2245 },
   { '?', '2', 0x2248 },
   { '=', '?', 0x224c },
+  { '.', '=', 0x2250 },
   { 'H', 'I', 0x2253 },
   { '!', '=', 0x2260 },
   { '=', '3', 0x2261 },