Review and add 21kHz at version 0.6.0. #491

.gitmodules

@@ -219,3 +219,6 @@
 [submodule "repos/FrankBussFormula"]
 	path = repos/FrankBussFormula
 	url = https://github.com/FrankBuss/Formula.git
+[submodule "repos/21kHz"]
+	path = repos/21kHz
+	url = https://github.com/21kHz/21kHz-rack-plugins.git

manifests/21kHz.json

@@ -0,0 +1,10 @@
+{
+    "name": "21kHz",
+    "author": "Jake Huryn",
+    "license": "MIT",
+    "authorEmail": "jakehuryn@gmail.com",
+    "manualUrl": "https://github.com/21kHz/21kHz-rack-plugins/blob/master/README.md",
+    "sourceUrl": "https://github.com/21kHz/21kHz-rack-plugins",
+    "donateUrl": "https://www.paypal.me/JakeHuryn",
+    "repoVersion": "0.6.0"
+}

repos/21kHz

@@ -0,0 +1 @@
+Subproject commit 622cf0f1c3e2de85f7008d8d27dae4ae18942c5e