Fixes issue #85 accuracy of birth weight

I have replaced the Slider input with a Textbox in which the user can accurately enter the weight of the baby. I have also taken care of the fact that user cannot enter decimal inputs as mentioned in the issue #85. There was no option to enter the weight of the baby in pounds as mentioned before as mentioned in the issue, so I have added a dropdown for the user to select whether he/she wants to enter the weight of the baby in pounds, and the entered value will be converted into weight in grams only, finally, which is the data that will go the backend.

Since this is a frontend change, I have atteached the video of the changed app down below,

Thank you, Shaunak Nagrechavideo_2023-03-03_15-50-45