Add people with git PRs to credits.

Add everyone who had a PR merged that changed the spec itself.

Author: timsifive

preface.tex

@@ -22,6 +22,7 @@ \chapter{Preface}
 Mark Beal,
 Alex Bradbury,
 Chuanhua Chang,
+Yen Hao Chen,
 Zhong-Ho Chen,
 Monte Dalrymple,
 Paul Donahue,
@@ -38,6 +39,8 @@ \chapter{Preface}
 Scott Johnson,
 L. J. Madar,
 Grigorios Magklis,
+Daniel Mangum,
+Alexis Marquet,
 Jan Matyas,
 Kai Meinhard,
 Jean-Luc Nagel,
@@ -50,9 +53,12 @@ \chapter{Preface}
 Ken Pettit,
 Darius Rad,
 Joe Rahmeh,
+Josh Scheid,
+Vedvyas Shanbhogue,
 Gavin Stark,
 Ben Staveley,
 Wesley Terpstra,
+Tommy Thorn,
 Megan Wachs,
 Jan-Willem van de Waerdt,
 Philipp Wagner,
@@ -61,4 +67,5 @@ \chapter{Preface}
 Andrew Waterman,
 Thomas Wicki,
 Andy Wright,
-and Bryan Wyatt.
+Bryan Wyatt,
+and Florian Zaruba.