feat: Added the Subjects Layout

[devrungta]

Description

• Added the subjects_screen.dart file for the subjects page.
• Added the required fields in the subject.dart model file.
• Added consistency throughout the app in terms of using user credentials.
• Added the Subjects Layout with add subject function.
• add subject function added in the firestore_services as well.
• Changed the Attendance Layout for border color changes as per required
• Removed the attendance.dart file and assets folder and integrated the API in the attendance and subjects to fetch the subjects from firestore.

Related Issue

Fixes #3 Feat #2 (Add Subjects part)

Type of Change

• [ ] Bug fix
• [x] New feature
• [x] Documentation update

Screenshots (if any):

Checklist

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [ ] My changes generate no new warnings

[Varun-Kolanu]

@devrungta Nice! Can you add something like an indicator in the addition of subject, when the user has chosen the days? Like highlighting the box of the day. One is confused whether he selected the day or not. And he should have the ability to undo his choice of day when again clicked..

And instead of full forms of days, shortforms would make the UI look good, being less clumsy. Then in the attendance page you can see if the day includes the day from the database instead of equating. Like, "Thursday".includes("Thur") will be true and hence show it on the home screen

[Varun-Kolanu]

Thanks working pretty well!