ARROW-4483: [Website] Add myself to contributors.yaml to fix broken link in blog post

Author: Andy Grove <andygrove73@gmail.com>

Closes #3564 from andygrove/ARROW-4483 and squashes the following commits:

0441126c2 <Andy Grove> Add myself to contributors.yaml to fix broken link in blog post
diff --git a/_data/contributors.yml b/_data/contributors.yml
index c492307..95b18b2 100644
--- a/_data/contributors.yml
+++ b/_data/contributors.yml
@@ -42,4 +42,8 @@
 - name: The Apache Arrow PMC
   apacheId: pmc
   githubId: pmc
+- name: Andy Grove
+  apacheId: agrove
+  githubId: andygrove
+  role: PMC
 # End contributors.yml