feat(lsp): support utf-8 and utf-32 position encodings

Resolves #30034

runtime/doc/news.txt

@@ -214,6 +214,7 @@ LSP
   clients.
 • |vim.lsp.buf.signature_help()| can now cycle through different signatures
   using `<C-s>` and also support multiple clients.
+• The client now supports `'utf-8'` and `'utf-32'` position encodings.
 
 LUA
 

runtime/lua/vim/lsp/protocol.lua

@@ -338,7 +338,9 @@ function protocol.make_client_capabilities()
   return {
     general = {
       positionEncodings = {
+        'utf-8',
         'utf-16',
+        'utf-32',
       },
     },
     textDocument = {