The removed section described `package_root` in a way which could be
interpreted that it is a configuration option for a testenv, whereas it
is a configuration option for the tox section, which is already
properly documented.

`lstrip` takes a set, not a string, so `.lstrip("-c ")` did not work as
intended.

Until we only support Python 3.9 or higher, we need to use a custom
function to remove a prefix. With Python 3.9+ we can use the builtin
`.removeprefix`.

This fixes #3247.

Co-authored-by: Bernát Gábor <gaborjbernat@gmail.com>

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Update test typing for build 1.2.0 which has an explicit Distribution type.

updates:
- [github.com/python-jsonschema/check-jsonschema: 0.28.0 → 0.28.1](python-jsonschema/check-jsonschema@0.28.0...0.28.1)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

* Update installation.rst

* Add changelog file

* Support __iadd__ in PythonDeps

* Allow appending to deps with -x testenv.deps+=foo

Fixes: #3256

---------

Co-authored-by: Bernát Gábor <gaborjbernat@gmail.com>

Currently only the last override supplied is considered, in conflict with now
supported append overrides ("+="). This now enables appending multiple times via
the command line.

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Co-authored-by: Asger Gitz-Johansen <asgj@gomspace.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>