[COMMITTERS] Add new committers agreed at today's TC meeting

In its meeting today, the OpenTitan Technical Committee took into
account the considerations described in
<https://docs.opentitan.org/doc/project/committers/> and voted to add
the additional committers listed in this patch.

Signed-off-by: Alex Bradbury <asb@lowrisc.org>
diff --git a/COMMITTERS b/COMMITTERS
index 3363586..8ebf49a 100644
--- a/COMMITTERS
+++ b/COMMITTERS
@@ -7,15 +7,23 @@
 
 Committer list:
 * Alex Bradbury (asb)
+* Greg Chadwick (gregac)
 * Cindy Chen (cindychip)
 * Timothy Chen (tjaychen)
+* Sam Elliott (lenary)
 * Srikrishna Iyer (sriyerg)
 * Scott Johnson (sjgitty)
+* Udi Jonnalagadda (udinator)
 * Garret Kelly (gkelly)
 * Eunchan Kim (eunchan)
 * Miguel Osorio (moidx)
 * Dominic Rizzo (domrizz0)
+* Tom Roberts (tomroberts-lowrisc)
 * Michael Schaffner (msfschaffner)
+* Silvestrs Timofejevs (silvestrst)
+* Alphan Ulusoy (alphan)
 * Pirmin Vogel (vogelpi)
 * Philipp Wagner (imphil)
+* Tobias Wölfel (towoe)
 * Weicai Yang (weicaiyang)
+* Miguel Young (mcy)