Add manifest.json, versions.json of Obsidian plugin to project root

- Obsidian provides limited support for plugins in larger repositories.
  Currently, it does not have a way to specify the directory of a plugin
  So it expects the plugins `manifest.json' and `versions.json' to be at
  project root

- While this unnecessarily litters the codebase. It is the (current)
  required tradeoff for keeping the core plugins in a mono repo

manifest.json

@@ -0,0 +1,10 @@
+{
+    "id": "khoj",
+    "name": "Khoj",
+    "version": "0.2.1",
+    "minAppVersion": "0.15.0",
+    "description": "Natural, Incremental Search for your Second Brain 🦅",
+    "author": "Debanjum Singh Solanky",
+    "authorUrl": "https://github.com/debanjum",
+    "isDesktopOnly": false
+}

versions.json

@@ -0,0 +1,3 @@
+{
+    "0.2.1": "0.15.0"
+}