Fix Roster filename and imports.

[vakhil-98]

Fixes #issue_number

What was changed? Fixed Roster.js and Roster.css filenames and imports.

Here, describe what part of the application you changed (e.g. login page, database, etc.). If possible, mention what specific components were added, removed, or modified. Fixes naming convention.

Why was it changed? Had used wrong spelling, fixed it.

Here, describe the issue that you are fixing with this code, and why your code fixes it.

How was it changed?

Here, get into detail about what files you modified, and talk about the most important lines in regards to fixing the issue. client_app/src/PastVolunteers.js, client_app/src/Roster.js, client_app/src/ShelterDashboard.js, client_app/src/ShiftContainer.js, client_app/src/styles/Roster.css

Screenshots that show the changes (if applicable):

[SiriChandanaGarimella]

hi @vakhil-98, could you please update it at the below lines as well

https://github.com/oss-slu/shelter_volunteers/blob/Fix_Roster_Filename/client_app/src/PastVolunteersContainer.js#L19 https://github.com/oss-slu/shelter_volunteers/blob/Fix_Roster_Filename/client_app/src/Roster.js#L5 https://github.com/oss-slu/shelter_volunteers/blob/Fix_Roster_Filename/client_app/src/Roster.js#L30 https://github.com/oss-slu/shelter_volunteers/blob/Fix_Roster_Filename/client_app/src/ShiftContainer.js#L2 https://github.com/oss-slu/shelter_volunteers/blob/Fix_Roster_Filename/client_app/src/ShiftContainer.js#L45 https://github.com/oss-slu/shelter_volunteers/blob/Fix_Roster_Filename/client_app/src/ShiftContainer.js#L47