Add a fuchsia trybot entry to mb_config.pyl.

tools/mb/mb_config.pyl

Index: tools/mb/mb_config.pyl
diff --git a/tools/mb/mb_config.pyl b/tools/mb/mb_config.pyl
index 210951c47789acd32331c0fe193055acd9ef96d7..16964cc2082fa2ccc4113c968ee37a431f827ce1 100644
--- a/tools/mb/mb_config.pyl
+++ b/tools/mb/mb_config.pyl
@@ -513,6 +513,7 @@
       'chromeos_daisy_chromium_compile_only_ng': 'cros_chrome_sdk',
       'chromeos_x86-generic_chromium_compile_only_ng': 'cros_chrome_sdk',
       'closure_compilation': 'closure_compilation',
+      'fuchsia': 'release_trybot_fuchsia',
       'linux_arm': 'release_trybot_arm',
       'linux_chromium_archive_rel_ng': 'release_bot',
       'linux_chromium_asan_rel_ng': 'asan_lsan_release_trybot',
@@ -1438,6 +1439,10 @@
       'release_trybot', 'arm',
     ],
 
+    'release_trybot_fuchsia': [
+      'release_trybot', 'fuchsia',
+    ],
+
     'release_trybot_x86': [
       'release_trybot', 'x86',
     ],