kaizen: Add CONTRIBUTING.md

Signed-off-by: Tim Bray <tbray@textuality.com>

CONTRIBUTING.md

@@ -0,0 +1,56 @@
+# Contributing to `Topfew`
+
+Topfew is hosted in this GitHub repository 
+at `github.com/timbray/topfew` and welcomes 
+contributions.
+
+As of mid-2024, Topfew is probably more or
+less complete. It is well-tested. Its performance at
+processing streams can keep up with most streams
+and it is dramatically faster when processing files,
+where it processes multiple segments in parallel.
+
+If you disagree and want to contribute to Topfew,
+the first step in making a change is typically to 
+raise an Issue to allow for discussion of the idea. 
+This is important because possibly Topfew already
+does what you want, in which case perhaps what’s 
+needed is a documentation fix. Possibly the idea 
+has been raised before but failed to convince Topfew’s
+maintainers. (Doesn’t mean it won’t find favor now;
+times change.)
+
+Assuming there is agreement that a change in Topfew
+is a good idea, the mechanics of forking the repository,
+committing changes, and submitting a pull request are
+well-described in many places; there is nothing 
+unusual about Topfew.
+
+### Code Style
+
+The coding style suggested by the Go community is 
+used in Topfew. See the
+[style doc](https://go.dev/wiki/CodeReviewComments) for details.
+
+Try to limit column width to 120 characters for both code and markdown documents
+such as this one.
+
+### Signing commits
+
+Commits should be signed (not just the `-s` “signd off on”) with
+any of the [styles GitHub supports](https://docs.github.com/en/authentication/managing-commit-signature-verification/signing-commits).
+Note that you can use `git config` to arrange that your commits are
+automatically signed with the right key.
+
+### Running Tests
+
+In the repository root `go test ./...` runs unit tests
+with all the defaults, which is a decent check for basic
+sanity and correctness.
+
+The following command runs the Go linter; submissions 
+need to be free of lint errors.
+
+```shell
+golangci-lint run  
+```