document some policies concerning contributions

Author: stephengold

CONTRIBUTING.md

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+# Contributing to Libbulletjme
+
+Thank you for your interest in contributing to Libbulletjme!
+
+The project isn't seeking financial contributions at this time.
+However, there are other ways you can contribute to Libbulletjme:
+
++ source code additions and improvements
+  (to the library, automated test suite, sample applications, or build scripts),
++ additions and improvements to the documentation,
++ bug reports,
++ suggestions,
++ comments on bug reports and suggestions submitted by others, and
++ publicity.
+
+Generally:
+
++ Anyone may contribute.
++ Contribute only your own work,
+  not the work of generative AI or other individuals.
++ No contribution is too small to be considered.
+
+In your communications, please be
+as kind, polite, generous, and grateful as you can.
+Comparison and criticism should be kept professional and impersonal.
+
+
+## Pull requests
+
+Contributions of source code and documentation should be submitted
+as GitHub pull requests to the relevent repository.
+Pull requests should always target the "master" branch.
+
+Each pull request should have a single, specific purpose.
+Never combine unrelated changes in a single pull request.
+
+Using static-analysis tools,
+it's possible to quickly generate large quantities of changes.
+Such changes will be considered on their merits.
+In my experience, however, static analysis rarely yields much value.
+The most valuable contributions come from people actively using the library,
+because users have insight into what's important and what isn't.
+
+Before editing the source code, please read relevant documentation, including
+[the implementation page](https://stephengold.github.io/Libbulletjme/lbj-en/English/implementation.html)
+and the "code style" section below.
+
+Before investing hours of effort in a pull request,
+please communicate with the project manager
+to determine whether the changes you envision are actually desired.
+Be open to advice on how to implement your idea.
+
+Contributed changes will be reviewed prior to integration.
+You can facilitate this process by explicitly requesting review
+when you think your pull request is ready.
+It's fine to question or discuss review comments.
+Multiple review passes may be needed; please be patient.
+
+
+### Code style
+
+Libbulletjme has an established code style for Java,
+which prioritizes readability and ease of maintenance
+over creativity and compactness.
+C++ source files, on the other hand, follow various styles,
+depending where they originated.
+Changes and exceptions to the prevailing style are discouraged.
+
+The style of Java sourcecode is loosely based on Google's published rules
+and is largely (but not entirely) enforced by Checkstyle.
+
+Project convention (not enforced by Checkstyle) determines the order
+of fields and methods within Java source files.
+Each file is divided into sections that appear a fixed sequence:
+
++ license
++ class Javadoc
++ constants
++ fields
++ constructors
++ new methods exposed (including native public methods)
++ new protected methods
++ override methods, grouped by superclass or interface
++ private methods
++ non-public native methods
+
+Within each section, methods are arranged alphanumerically:
+by name and then by argument types.
+Constants and fields are also arranged alphanumerically within sections:
+by type and then by name.
+
+
+## Conclusions
+
+Thanks for your attention. Your cooperation will be appreciated!