feat: make it easier to disable luarocks

lua/lazy/core/config.lua

@@ -41,11 +41,12 @@ M.defaults = {
     -- the first package source that is found for a plugin will be used.
     sources = {
       "lazy",
-      "rockspec",
+      "rockspec", -- will only be used when rocks.enabled is true
       "packspec",
     },
   },
   rocks = {
+    enabled = true,
     root = vim.fn.stdpath("data") .. "/lazy-rocks",
     server = "https://nvim-neorocks.github.io/rocks-binaries/",
   },

lua/lazy/pkg/init.lua

@@ -32,11 +32,13 @@ function M.update()
   ---@type LazyPkgSource[]
   local sources = {}
   for _, s in ipairs(Config.options.pkg.sources) do
+    if s ~= "rockspec" or Config.options.rocks.enabled then
       sources[#sources + 1] = {
         name = s,
         get = require("lazy.pkg." .. s).get,
       }
     end
+  end
 
   ---@type LazyPkgCache
   local ret = {