Adopting spec 0 (#788)

Author: sjsrey

README.md

@@ -6,6 +6,7 @@
 [![Conda Version](https://img.shields.io/conda/vn/conda-forge/libpysal.svg)](https://anaconda.org/conda-forge/libpysal)
 [![DOI](https://zenodo.org/badge/81501824.svg)](https://zenodo.org/badge/latestdoi/81501824)
 [![Discord](https://img.shields.io/badge/Discord-join%20chat-7289da?style=flat&logo=discord&logoColor=cccccc&link=https://discord.gg/BxFTEPFFZn)](https://discord.gg/BxFTEPFFZn)
+[![SPEC 0 — Minimum Supported Dependencies](https://img.shields.io/badge/SPEC-0-green?labelColor=%23004811&color=%235CA038)](https://scientific-python.org/specs/spec-0000/)
 
 ## libpysal modules