add missing externs to repo

externs/webextension_polyfill/theme/Static.hx

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+package webextension_polyfill.theme;
+
+typedef Static = {
+	/**
+		Returns the current theme for the specified window or the last focused window.
+	**/
+	function getCurrent(?windowId:Float):js.lib.Promise<Dynamic>;
+	/**
+		Make complete updates to the theme. Resolves when the update has completed.
+		
+		Make complete updates to the theme. Resolves when the update has completed.
+	**/
+	@:overload(function(details:webextension_polyfill.manifest.ThemeType):js.lib.Promise<ts.Undefined> { })
+	function update(windowId:Null<Float>, details:webextension_polyfill.manifest.ThemeType):js.lib.Promise<ts.Undefined>;
+	/**
+		Removes the updates made to the theme.
+	**/
+	function reset(?windowId:Float):js.lib.Promise<ts.Undefined>;
+	/**
+		Fired when a new theme has been applied
+	**/
+	var onUpdated : webextension_polyfill.events.Event<(updateInfo:ThemeUpdateInfo) -> Void>;
+};

externs/webextension_polyfill/theme/ThemeUpdateInfo.hx

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+package webextension_polyfill.theme;
+
+/**
+	Info provided in the onUpdated listener.
+**/
+typedef ThemeUpdateInfo = {
+	/**
+		The new theme after update
+	**/
+	var theme : ThemeUpdateInfoThemeType;
+	/**
+		The id of the window the theme has been applied to
+		Optional.
+	**/
+	@:optional
+	var windowId : Float;
+};

externs/webextension_polyfill/theme/ThemeUpdateInfoThemeType.hx

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+package webextension_polyfill.theme;
+
+/**
+	The new theme after update
+**/
+typedef ThemeUpdateInfoThemeType = { };