new local scheme of dirty-tag for developer installation (#191)

## Description
When we install RecordLinker into an environment, a version number is
automatically calculated from git data using setuptools scm. If the HEAD
is a version tag, then the version is automatically calculated to be
that. In development environments, though, we take the last version and
add a "post.0" to it, showing it's a new release post the last named
one.

Additionally, we were previously calculating a timestamp to add to that
"post.0" value based on when HEAD was committed. This worked most of the
time, however if the developer has a dirty index, the wheel wouldn't
build correctly. We don't need that, and it's fine if a developer tries
to install / reinstall RecordLinker in an environment with a dirty
index. So to get around that, we'll stop adding the timestamp to the end
of "post.0" and instead just call it "post.0+dirty" (if the index is
indeed dirty).

pyproject.toml

@@ -73,7 +73,7 @@ namespaces = false
 [tool.setuptools_scm]
 write_to = "src/recordlinker/_version.py"
 version_scheme = "post-release"
-local_scheme = "node-and-timestamp"
+local_scheme = "dirty-tag"
 fallback_version = "0.0.0"
 
 [tool.ruff]