Replace submodule with direct copy of one.el fork for Docker compatibility

one.el/README.org

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+~one.el~ a simple Static Site Generator for Emacs Lisp programmers and
+org-mode users.
+
+Check the docs: https://one.tonyaldon.com.
+
+Note that the docs are built using ~one.el~ itself.  To build them,
+visit [[./docs/docs.org]] and call ~one-build~ command.  This will build the
+docs under ~./docs/public/~ subdirectory.
+
+To run the tests, visit [[./one-tests.el]] and call the ~eval-buffer~
+and ~ert~ commands like this:
+
+- M-x eval-buffer
+- M-x ert RET RET
+
+Check the [[./LICENSE]].