Update contribution guidelines

CONTRIBUTING.md

@@ -47,21 +47,25 @@ Contributing
 
 GeoMesa uses git pull requests for contributions. To create a pull request, follow these steps:
 
-* Contributions to GeoMesa must reference a valid JIRA ticket. Contact the GeoMesa developers list
-  about opening a ticket, or to have a ticket assigned to you.
+* Before starting work, reach out to the community via the [developers list](https://accounts.eclipse.org/mailing-list/geomesa-dev)
+  or on [Gitter](https://gitter.im/locationtech/geomesa) to ensure the contribution aligns with the project's goals.
+* Most contributions must reference a valid JIRA ticket, unless the change is very small. Sign up for an account at
+  https://geomesa.atlassian.net/issues/?jql= and self-assign a ticket. Alternatively, contact the
+  [developers list](https://accounts.eclipse.org/mailing-list/geomesa-dev) about doing it for you.
+* Ensure that you have signed the Eclipse CLA with the email associated with your GitHub account:
+  https://www.eclipse.org/legal/ECA.php
 * Fork the GeoMesa project on GitHub - go to https://github.com/locationtech/geomesa and click 'Fork'.
 * Create a branch on your forked project that contains your work. See 'Coding Standards', below.
 * Use GitHub to open a pull request against the locationtech GeoMesa repository - from your branch on
   GitHub, click 'New Pull Request'.
 * Respond to comments on your pull request as they are made.
-* When ready, your pull request will be merged by an official GeoMesa contributor.
+* When ready, your pull request will be merged by a GeoMesa committer.
 
 Coding Standards
 ----------------
 
-* An initial pull request should consist of a single commit, rebased on top of the current main branch.
-  * Additional commits can be added in response to code review comments.
-* The commit message must consist of a JIRA ticket number followed by a short description, with additional
+* An initial pull request should be up-to-date with the current main branch.
+* The pull request title should consist of a JIRA ticket number followed by a short description, with additional
   information in bullets below as required.
   * See e.g. https://github.com/locationtech/geomesa/commit/1f345132a717816d5a4951f73b2b73537fce305b
 * Code must be reasonably formatted. Scala does not conform well to automatic formatting, but in general