docs(wpcarro/emacs): Document list.el

- Add README.md
- Remove stale TODOs
- Rephrase some of the module docs

Change-Id: I14002836feeca4dd702350151b64600ea2a9125d
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6042
Reviewed-by: wpcarro <wpcarro@gmail.com>
Autosubmit: wpcarro <wpcarro@gmail.com>
Tested-by: BuildkiteCI

users/wpcarro/emacs/pkgs/list/README.md

@@ -0,0 +1,19 @@
+# list.el
+
+Functions for working with lists in Elisp.
+
+## Wish List
+
+Here are some additional functions that I'd like to support.
+
+-  **TODO**: delete_at/2
+-  **TODO**: flatten/1
+-  **TODO**: flatten/2
+-  **TODO**: foldl/3
+-  **TODO**: foldr/3
+-  **TODO**: insert_at/3
+-  **TODO**: pop_at/3
+-  **TODO**: replace_at/3
+-  **TODO**: starts_with?/2
+-  **TODO**: update_at/3
+-  **TODO**: zip/1