Text descriptions about `Error Handlers` are not very friendly to novices.
https://docs.python.org/3/library/codecs.html#error-handlers

For example:

    'xmlcharrefreplace'
    Replace with the appropriate XML character reference (only for encoding).  Implemented in :func:`xmlcharrefreplace_errors`. 

    'backslashreplace'
    Replace with backslashed escape sequences. Implemented in :func:`backslashreplace_errors`.

    'namereplace'
    Replace with ``\N{...}`` escape sequences (only for encoding).  Implemented in :func:`namereplace_errors`.

Novices may not know what these are.
Giving some examples may help the reader to understand more intuitively.
The effect picture is attached.

I picked two characters:
ß  https://www.compart.com/en/unicode/U+00DF
♬ https://www.compart.com/en/unicode/U+266C

PR 15732 became an overhaul:

- replace/backslashreplace/surrogateescape were wrongly described as encoding only, in fact they can also be used in decoding.
- clarify the description of surrogatepass.
- add more descriptions to each handler.
- add two REPL examples.
- add indexes for Error Handler's name.
- add default parameter values in codecs.rst
- improve term "text encoding".

PR 15732 has a screenshot of the Error Handlers section.