add: download all notes of tag

main.js

@@ -183,6 +183,10 @@ var commands = [
 	action: downloadnotes,
 	shortcut: "ctrl+shift+S"
 },
+{
+	hint: "Download all notes of tag (md files in zip archive)",
+	action: downloadtag
+},
 {
 	hint: "Download all notes (html files in zip archive)",
 	action: downloadhtmlnotes
@@ -1006,6 +1010,27 @@ function download(filename, content)
 	element = null;
 }
 
+function downloadtag()
+{
+	tagslist()
+	.then(tag =>
+	{
+		var zip = new JSZip();
+		Object.keys(metadata).forEach(guid =>
+		{
+			if (metadata[guid].header.tags.includes(tag))
+			{
+				zip.file(getfilename(metadata[guid].title), localStorage.getItem(guid));
+			}
+		});
+		zip.generateAsync({type:"blob"})
+		.then(function(content)
+		{
+			saveAs(content, "notes-" + tag + "=" + timestamp() + ".zip");
+		});
+	});
+}
+
 function downloadnotes()
 {
 	var zip = new JSZip();