[Piglit] access to use marge bot

[Eleni Maria Stea]

Hello,

It's been some time I am doing contributions to piglit (most recent
ones are my Vulkan helper functions and tests for EXT_external_objects
in tests/spec/ext_external_objects/). 

I was wondering if I could be given access to use Marge bot so that I
don't have to ask my reviewers to merge my patches every time they
approve a change I've submitted. 

My total number of contributions at this moment is 18 but if they
aren't enough for the Marge bot access, sorry in advance for the noise!
:)

Thanks a lot!
Eleni