Vendor libs/hump, sfxrlua, json4lua, narrator as real files

These were committed as empty submodule gitlinks with no .gitmodules,
so the folders were never populated and the game could not load
(require of libs/hump/timer, libs/sfxrlua/sfxr, narrator.narrator).
Checked out each at its pinned commit and vendored the files, matching
the existing bundled-libs convention. Removed the junk libs/libs/ tree.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

libs/json4lua/examples/example.lua

@@ -0,0 +1,23 @@
+--[[
+JSON4Lua example script.
+Demonstrates the simple functionality of the json module.
+]]--
+json = require('json')
+
+
+-- Object to JSON encode
+test = {
+  one='first',two='second',three={2,3,5}
+}
+
+jsonTest = json.encode(test)
+
+print('JSON encoded test is: ' .. jsonTest)
+
+-- Now JSON decode the json string
+result = json.decode(jsonTest)
+
+print ("The decoded table result:")
+table.foreach(result,print)
+print ("The decoded table result.three")
+table.foreach(result.three, print)