Fix registration form accessibility

Currently the Registration Form on the [Events](https://codingblocks.com/events/) page doesn't have any labels. They just rely on placeholders.

Firefox Accessibility checker reports this issue and it is a well known UX practice to keep label.

I can fix the accessibility bug by adding labels and linking them with proper inputs. UI would something like this

Open the Events page and inspect the Registration Form markup, starting with the fields identified by Firefox Accessibility checker. Add visible labels associated with the corresponding inputs, then verify the form in Firefox's accessibility checker and confirm the existing layout and behavior remain intact.

Written by the indexing model from the issue text.