feat: vendor GYP and libuv dependencies directly into repository for offline builds

Remove dynamic dependency download during build by checking in libuv source and GYP build tooling. Update .gitignore to exclude intermediate build artifacts from the vendored deps directory, adjust Makefile to remove the now-unnecessary cleanall target and deps folder cleanup, and add the full libuv project tree including its own .gitignore, .mailmap, AUTHORS, CONTRIBUTING.md, ChangeLog, and LICENSE files.

Makefile

@@ -11,9 +11,10 @@ endif
 # Executables are built to bin/. Libraries are built to lib/.
 
 # A normal, optimized release build for the current CPU architecture.
+# For convenience, also copies the interpreter to the top level.
 release:
 	$(V) $(MAKE) -f util/wren.mk
-	$(V) cp bin/wren wren # For convenience, copy the interpreter to the top level.
+	$(V) cp bin/wren wren
 
 # A debug build for the current architecture.
 debug:
@@ -74,10 +75,6 @@ clean:
 	$(V) rm -rf build
 	$(V) rm -rf lib
 
-# Remove all build outputs, intermediate files, and downloaded dependencies.
-cleanall: clean
-	$(V) rm -rf deps
-
 # Run the tests against the debug build of Wren.
 test: debug
 	$(V) $(MAKE) -f util/wren.mk MODE=debug test