Added: Adds Zenodo DOI badge and identifier

Adds a Zenodo DOI badge to the README and a Zenodo concept DOI
identifier to the CITATION.cff file to improve discoverability
and citation of the la-stack project.

Author: acgetchell

CITATION.cff

@@ -5,6 +5,10 @@ title: "la-stack: Fast, stack-allocated linear algebra for fixed dimensions in R
 version: 0.1.2
 url: "https://github.com/acgetchell/la-stack"
 repository-code: "https://github.com/acgetchell/la-stack"
+identifiers:
+  - description: "Zenodo concept DOI (all versions)"
+    type: doi
+    value: "10.5281/zenodo.18158926"
 authors:
   - family-names: "Getchell"
     given-names: "Adam"

README.md

@@ -1,5 +1,6 @@
 # la-stack
 
+[![DOI](https://zenodo.org/badge/DOI/10.5281/zenodo.18158926.svg)](https://doi.org/10.5281/zenodo.18158926)
 [![Crates.io](https://img.shields.io/crates/v/la-stack.svg)](https://crates.io/crates/la-stack)
 [![Downloads](https://img.shields.io/crates/d/la-stack.svg)](https://crates.io/crates/la-stack)
 [![License](https://img.shields.io/crates/l/la-stack.svg)](./LICENSE)