[MRG] Add GSoC link to Contr page (#1234)

This also adds some instruction about "don't make duplicate PRs".

Because GSoC is ramping up, I will self-merge this PR as soon as it
passes the tests. I will then take the up-to-date "dev" version of the
Contributing Guide page, and overwrite the "stable" documentation
version of the same page. This way, the GSoC link will be on the
primary, published Contributing page.

Author: asoplata

doc/contributing.md

@@ -3,19 +3,37 @@
 
 Please read the contribution guide **until the end** before beginning contributions.
 
-Contributions are welcome in the form of Pull Requests. You must abide by our [Code of
+Contributions are welcome in the form of Pull Requests (PR's). You must abide by our [Code of
 Conduct, found
-here](https://github.com/jonescompneurolab/hnn-core/blob/master/CODE_OF_CONDUCT.md), which includes instructions on what kind of AI- and LLM-generated code contributions we accept. Our
-{doc}`Governance Model can be found here <governance>`. Please tie your Pull Requests to specific Issues.
-
-Once the implementation of a piece of functionality is considered to be bug free and
-properly documented (both API docs and an example script), it can be incorporated into
-the `master` branch, which is where our releases come from.
-
-To contribute to `hnn-core` development, you need a special kind of installation, see the
-["`pip` Source Installation" section of our Installation Guide][] on our [Textbook website][]. Note that this is **different** from the "`pip` Package Installation" type on that webpage!
-
-We are experimenting with having once-monthly HNN Development meetings which are open to the public. These take place on the first Monday of every month at 1:00 PM, United States Eastern time (the [timezone of Providence, RI, viewable here](https://www.timeanddate.com/worldclock/usa/providence)). You can access the Zoom room here [https://brown.zoom.us/j/99212200748](https://brown.zoom.us/j/99212200748). Note that there is a waiting room and you *must raise your hand* before you will be granted audio privileges. We reserve the right to kick out anyone causing disruptions during the meeting.
+here](https://github.com/jonescompneurolab/hnn-core/blob/master/CODE_OF_CONDUCT.md),
+which includes instructions on what kind of AI- and LLM-generated code contributions we
+accept. Our {doc}`Governance Model can be found here <governance>`.
+
+Please **double-check that your new Pull Request does not accomplish the same task as
+any existing Pull Request**! We reserve the right to close any new PRs that are
+"duplicates" of work (and any PR in general). Please tie your Pull Requests to specific
+Issues. Once the implementation of a piece of functionality is considered to be bug free
+and properly documented (both API docs and possibly an example script), and we have
+reviewed it, we may merge it into the `master` branch, which is where our releases come
+from.
+
+If you are interested in contributing to `hnn-core` as part of Google Summer of Code
+2026, [please see the Issue here for the latest
+information](https://github.com/jonescompneurolab/hnn-core/issues/1202).
+
+To contribute to `hnn-core` development, you need a special kind of installation, see
+the ["`pip` Source Installation" section of our Installation Guide][] on our [Textbook
+website][]. Note that this is **different** from the "`pip` Package Installation" type
+on that webpage!
+
+We are experimenting with having once-monthly HNN Development meetings which are open to
+the public. These take place on the first Monday of every month at 1:00 PM, United
+States Eastern time (the [timezone of Providence, RI, viewable
+here](https://www.timeanddate.com/worldclock/usa/providence)). You can access the Zoom
+room here
+[https://brown.zoom.us/j/99212200748](https://brown.zoom.us/j/99212200748). Note that
+there is a waiting room and you *must raise your hand* before you will be granted
+audio/video privileges. We will kick out anyone causing disruptions during the meeting.
 
 ## How to contribute code