DOC: add SPEC 8 badge

Author: lucascolley

Diff for: README.md

@@ -11,6 +11,8 @@
 [![Conda-Forge][conda-badge]][conda-link]
 [![PyPI platforms][pypi-platforms]][pypi-link]
 [![EffVer Versioning](https://img.shields.io/badge/version_scheme-EffVer-0097a7)](https://jacobtomlinson.dev/effver)
+[![SPEC 0 — Minimum Supported Dependencies](https://img.shields.io/badge/SPEC-0-green?labelColor=%23004811&color=%235CA038)](https://scientific-python.org/specs/spec-0000/)
+
 
 <!-- SPHINX-START -->