Update README to mention new CONTRIBUTING document
Update README to mention new CONTRIBUTING document

[ci skip]

Signed-off-by: BJ Hargrave <3d26bb3930946e3370762d769a073cece444c2d8@bjhargrave.com>

timothyjward/bndtools,njbartlett/bndtools,bndtools/bndtools,lostiniceland/bndtools,timothyjward/bndtools,lostiniceland/bndtools,lostiniceland/bndtools,grfield/bndtools,seanbright/bndtools,bndtools/bndtools,psoreide/bnd,bjhargrave/bndtools,njbartlett/bndtools,njbartlett/bndtools,bndtools/bndtools,wodencafe/bndtools,psoreide/bnd,seanbright/bndtools,psoreide/bnd,njbartlett/bndtools,grfield/bndtools,pkriens/bndtools,njbartlett/bndtools,seanbright/bndtools,bndtools/bndtools,lostiniceland/bndtools,bjhargrave/bndtools,pkriens/bndtools,seanbright/bndtools,wodencafe/bndtools,pkriens/bndtools,pkriens/bndtools,lostiniceland/bndtools,grfield/bndtools,wodencafe/bndtools,timothyjward/bndtools,bjhargrave/bndtools,bjhargrave/bndtools,lostiniceland/bndtools,wodencafe/bndtools,wodencafe/bndtools,bjhargrave/bndtools,grfield/bndtools,bjhargrave/bndtools,njbartlett/bndtools,pkriens/bndtools,pkriens/bndtools,timothyjward/bndtools,timothyjward/bndtools,bndtools/bndtools,seanbright/bndtools,grfield/bndtools,wodencafe/bndtools