Build MV3 variant for Chrome's beta channel

In order to begin testing the MV3 variant in the beta channel
distributed in the Chrome Web Store.

Change-Id: I0dad1f3b5e3b3b0b17fe2e88ce7b7212f2cfcc83
diff --git a/Makefile b/Makefile
index 3fdb95e..4b501c0 100644
--- a/Makefile
+++ b/Makefile
@@ -41,9 +41,9 @@
 	rm -rf dist/chromium
 release_chromium_beta: deps
-	$(WEBPACK) --mode production --env browser_target=chromium
-	$(RELEASE_SCRIPT) -c beta -b chromium
-	rm -rf dist/chromium
+	$(WEBPACK) --mode production --env browser_target=chromium_mv3
+	$(RELEASE_SCRIPT) -c beta -b chromium_mv3
+	rm -rf dist/chromium_mv3
 release_gecko_stable: deps
 	$(WEBPACK) --mode production --env browser_target=gecko
diff --git a/docs/developers/ b/docs/developers/
index 9fe8e75..f9b35f1 100644
--- a/docs/developers/
+++ b/docs/developers/
@@ -35,14 +35,12 @@
 manually in Chrome (but at least you won't have to both build and reload it).
 ## About the _Chromium MV3_ target
-Chromium is working in a
+Chromium announced a while back a
 [new version of the manifest.json file](,
-which also introduces some changes to the extension APIs. Eventually, all Chrome
-extensions will be required to have migrated to Manifest V3 (MV3), so in order
-to anticipate this change, a new experimental _Chromium MV3_ target has been
+which also introduces some changes to the extension APIs. The _Chromium MV3_
+target builds the extension using this new version.
-This target is experimental in the sense that it isn't actually used when
-building the extension ZIPs which are uploaded to the Chrome Web Store (MV2 is
-still used), and because these builds aren't currently being exhaustively
+[MV2 will phase out in January 2023](,
+so starting with version v2.1.2, the CWS beta channel will receive the MV3
+variant of the extension to begin testing it publicly. For now, the stable
+channel will continue to receive the MV2 variant of the extension.