Improve tensor handling in live detection

Signed-off-by: Justin Georgi <justin.georgi@gmail.com>

src/pages/detection-mixin.js

@@ -222,6 +222,9 @@ export default {
               imageCtx.drawImage(target, pointX, pointY, 20, 20)
             }
           }
+          tf.dispose(input)
+          tf.dispose(res)
+          tf.dispose(rawRes)
         } catch (e) {
           console.log(e)
         }