fixes: #76bug add validation for all input field's

[love-sonkar]

fixes #76 added validation in all input field's and for the category i use a dropdown selection for better user experiance and for validation.

[MayankBansal12]

• Make sure all the functions are working properly.
• After making the changes, make sure the code is not broken or getting affected due to changes. - Also, try to check everything is working by adding a few entries from your end.

[KendallDoesCoding]

@MayankBansal12 are we good to merge?

[love-sonkar]

yes we can merge this PR

[MayankBansal12]

You only need to modify the add categories. Other than that, everything else looks good.

[KendallDoesCoding]

@love-sonkar - thanks for your contribution!