Docs: Update readme

[phil-s]

Per (info "(org)Escape Character") I've introduced a zero-width space before the closing paren in "(while writing in minibuffer: ~C-c '~​)" in order to achieve the correct formatting. This can be visualised using (set-face-background 'glyphless-char "red").

I've substitutedS-<return> everywhere that S-RET appeared, as the latter isn't a valid representation.

[phil-s]

Darn, Github doesn't like what I did with the C-c ' formatting!

https://github.com/phil-s/ement.el/tree/phil-s/docs?tab=readme-ov-file#room-buffers

I'll see if I can figure out a fix for that...

[phil-s]

That was a pain -- I think I now understand why the text had previously been written as C-c ') !

Through trial-and-error I've found that a single ZERO WIDTH JOINER after the apostrophe in C-c '‍ works for both Emacs and Github, so I've pushed that fix.

[alphapapa]

Thank you.