bug#61051: treesit-install-language-grammar can provide the default repository URL

[Dmitry Gutov]

The format https://github.com/tree-sitter/tree-sitter-%s will work for a 
lot of languages, and the user won't even have to search for the address.

The patch can look like this:

diff --git a/lisp/treesit.el b/lisp/treesit.el
index 660039cc7cc..c1b98d085e8 100644
--- a/lisp/treesit.el
+++ b/lisp/treesit.el
@@ -2708,7 +2708,8 @@ treesit--install-language-grammar-build-recipe
       (list
        lang
        (read-string
-        "Enter the URL of the Git repository of the language grammar: ")
+        "Enter the URL of the Git repository of the language grammar: "
+        (format "https://github.com/tree-sitter/tree-sitter-%s"; lang))
        (empty-string-to-nil
         (read-string
          "Enter the tag or branch (default: default branch): "))