Update authors file with new developers.

[MFraters]

I didn't realize this authors file was aready here, so I update this to match the info in the readme.

[gassmoeller]

👍

[github-actions]

Benchmark	Main	Feature	Difference (99.9% CI)
Slab interpolation simple none	1.134 ± 0.013 (s=387)	1.147 ± 0.014 (s=404)	+0.9% .. +1.4%
Slab interpolation curved simple none	1.119 ± 0.009 (s=404)	1.135 ± 0.012 (s=397)	+1.3% .. +1.7%
Spherical slab interpolation simple none	1.095 ± 0.009 (s=400)	1.104 ± 0.008 (s=421)	+0.7% .. +1.0%
Slab interpolation simple curved CMS	1.167 ± 0.011 (s=407)	1.180 ± 0.011 (s=363)	+0.9% .. +1.3%
Spherical slab interpolation simple CMS	1.446 ± 0.014 (s=330)	1.458 ± 0.012 (s=292)	+0.6% .. +1.1%
Spherical fault interpolation simple none	1.100 ± 0.011 (s=419)	1.113 ± 0.011 (s=397)	+0.9% .. +1.4%
Cartesian min max surface	2.541 ± 0.021 (s=210)	2.569 ± 0.021 (s=145)	+0.8% .. +1.4%
Spherical min max surface	7.157 ± 0.087 (s=69)	7.246 ± 0.100 (s=59)	+0.5% .. +2.0%