This PR adds an optional argument to the `|tojson` filter, which
controls if the serialized JSON data gets prettified or not. The
arguments works the same as flask's [`|tojson`][flask] filter, which
passes the argument to python's [`json.dumps()`][python]:
* Omitting the argument, providing a negative integer, or `None`, then
compact JSON data is generated.
* Providing a non-negative integer, then this amount of ASCII spaces is
used to indent the data. (Capped to 16 characters.)
* Providing a string, then this string is used as prefix. I attempts are
made to ensure that the prefix actually consists of whitespaces,
because chances are, that if you provide e.g. `&nsbp;`, then you are
doing it intentionally.
This is a breaking change, because it changes the default behavior to
not prettify the data. This is done intentionally, because this is how
it works in flask.
[flask]: https://jinja.palletsprojects.com/en/3.1.x/templates/#jinja-filters.tojson
[python]: https://docs.python.org/3/library/json.html#json.dump
`std::fmt::Error` does not know why it failed, only that it failed, as
it has a single value. This PR removes the captured value, to make the
code a bit more dense.
