add: the description of 2 endpoints in backend

packages/elysia/routes/root/index.ts

@@ -53,7 +53,8 @@ export const rootHandler = new Elysia().get(
 		},
 		detail: {
 			summary: "Root route",
-			description: ""
+			description: "The root path. It returns a JSON object containing a random virtual singer, \
+			backend version, current server time and other miscellaneous information."
 		}
 	}
 );

packages/elysia/routes/song/info.ts

@@ -88,7 +88,11 @@ export const getSongInfoHandler = new Elysia({ prefix: "/song" }).get(
 		},
 		detail: {
 			summary: "Get information of a song",
-			description: ""
+			description: "This endpoint retrieves detailed information about a song using its unique ID, \
+			which can be provided in several formats. \
+			The endpoint accepts a song ID in either a numerical format as the internal ID in our database\
+			 or as a bilibili video ID (either av or BV format). \
+			 It responds with the song's name, bilibili ID (av), producer, duration, and associated singers."
 		}
 	}
 );