Nahiyan_Dark mode on dropdown items

[Nahiyan-16]

Description

Dark mode is implemented on all dropdown items on the header

Related PRS (if any):

This frontend PR is related to the dev backend

How to test:

1. check into current branch
2. do npm install and npm run start:local to run this PR locally
3. Clear site data/cache
4. log as owner
5. go to any page besides the dashboard or timelog page (They seem to be broken in development)
6. Once you can see the header, select on reports, other links and welcome dropdowns.
7. verify dark mode is working properly both in light mode and dark

Screenshots or videos of changes:

[Vijeth-V]

Good job Nahiyan, this works perfectly well.

[cvtqx]

All the drop down elements look dark in dark mode and light in light mode, just as expected.

Video:
https://github.com/OneCommunityGlobal/HighestGoodNetworkApp/assets/107726913/25803993-6515-4d18-8ba2-961fcd13fcc6

[Logeshwari-Renu]

I have tested the PR and the dark mode works on the Reports, Other links and User dropdowns available in the header.
When switched back to Light mode the dropdown changes to light colour.
The Functionality for dark mode on dropdown in headers works fine!

[aaryaneil]

Tested the PR and the changes work as expected. Added screenshots for light and dark mode drop down menus.

[tianyangL11]

Great！ It work as expected

[KurtisIvey]

I might come across as a stickler for this one, but i'm requesting changes for two reasons.

1. the "hello username" is in the same font color as the actual drop down selector links. It should be lighter or modified to a less intuitively interactive color as it is in light mode.
   

2. There's no reason to lighten the text as the hover color activates. Normally, text lightens in color when in dark mode and hovered upon. Just leave the text color as white, so the contrast ratio doesn't get worse at the very least.
   

[KurtisIvey]

Changes look great. If you can clear up the merge conflict please and then shoot me a slack message once it's done, so I can review it again when I get off work.

[KurtisIvey]

Everything checks out after clearing up the merge conflict. Great Job!