fix(config): convert static values to dynamic functions

- Modified "host" and "user" to use function calls
- Updated "gh-email" and "gh-user" to use function calls
- These changes ensure that the values are always up-to-date when
  accessed, rather than being set once at initialization
- This reduces startuptime of plugin from ~30ms to ~3ms (10x
  improvement)

lua/esqueleto/config.lua

@@ -24,12 +24,12 @@ M.default_config = {
       ["time"] = function() return os.date("%T", os.time()) end,
 
       -- System
-      ["host"] = utils.capture("hostname", false),
-      ["user"] = os.getenv("USER"),
+      ["host"] = function() return utils.capture("hostname", false) end,
+      ["user"] = function() return os.getenv("USER") end,
 
       -- Github
-      ["gh-email"] = utils.capture("git config user.email", false),
-      ["gh-user"] = utils.capture("git config user.name", false),
+      ["gh-email"] = function() return utils.capture("git config user.email", false) end,
+      ["gh-user"] = function() return utils.capture("git config user.name", false) end,
     },
   },
   advanced = {