fixed CITATION.cff to show DOI (#676)

* fixed CITATION.cff to show DOI

* Fix formatting in README.md for citation entry

Author: cwittens

CITATION.cff

@@ -1,10 +1,8 @@
-# This CITATION.cff file was generated with cffinit.
-# Visit https://bit.ly/cffinit to generate yours today!
-
 cff-version: 1.2.0
 title: KernelAbstractions.jl
 message: 'If you use this software, please cite it as below.'
 type: software
+doi: 10.5281/zenodo.4021259
 authors:
   - family-names: Churavy
     given-names: Valentin

README.md

@@ -46,7 +46,7 @@ Cite this package as
 author = {Churavy, Valentin},
 license = {MIT},
 title = {{KernelAbstractions.jl}},
-url = {https://github.com/JuliaGPU/KernelAbstractions.jl}
-doi = {10.5281/zenodo.4021259},
+url = {https://github.com/JuliaGPU/KernelAbstractions.jl},
+doi = {10.5281/zenodo.4021259}
 }
 ```