Added mgiuca and thakis as OWNERS of .git-blame-ignore-revs.
Added mgiuca and thakis as OWNERS of .git-blame-ignore-revs.

This is to reduce burden on top-level owners of approving additions to
this file, and so we can enforce somewhat of a standard bar for what
goes into the hyper-blame ignore list.

BUG=574290

Review URL: https://codereview.chromium.org/1724383002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#377223}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk