Add news about sunsetting Mambaforge

news/2024-07-29-sunsetting-mambaforge.md

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+# Sunsetting Mambaforge
+
+With the [Miniforge 23.3.1 release](https://github.com/conda-forge/miniforge/releases/tag/23.3.1-0),
+the Miniforge and Mambaforge installers became essentially **identical**. The only difference
+between the two was their name and, subsequently, the default installation directory.
+
+Maintaining both installers adds unnecessary burden to our support infrastructure and creates
+confusion among end users. As a result, last year we decided to _discourage_ the usage of
+Mambaforge in favor of Miniforge.
+
+A year later, we would like to formally sunset Mambaforge. All users are encouraged to switch to
+Miniforge. Remember they contain the same packages, so the only difference is the default
+installation directory.
+
+The deprecation process will roughly follow this calendar:
+
+- August 2024: The Mambaforge installers will warn about the deprecation and make the user wait 30
+  seconds before continuing.
+- October 2024: The Mambaforge installers will refuse to install during several pre-specified date ranges (i.e., ["brownouts"](<https://en.wikipedia.org/wiki/Brownout_(software_engineering)>)) in order to encourage users to switch to Miniforge. These dates are
+  - Every two weeks in October 2024 (2024-10-01, 2024-10-15)
+  - Every ten days in November 2024 (2024-11-01, 2024-11-10, 2024-11-20, 2024-11-30)
+  - Every five days in December 2024 (2024-12-05, 2024-12-10, 2024-12-15, 2024-12-20, 2024-12-25, 2024-12-30, 2024-12-31)
+- January 2025: The Mambaforge installers will stop being built and distributed.