Screenshots Update revised in README.md

[ManishS6]

Fixes #(issue number)

442

Describe the changes you've made

I have changed the screenshots as discussed in #444 also have added screenshots corresponding to the following pages

1. Sign up page
2. Forgot Password Page
3. Feedback Page
4. Dark themed help page

Describe if there is any unusual behaviour of your code(Write NA if there isn't)

NA

Deploy your changes to github page or netlify and mention deployment link:

NA

Checklist

• [x] I have mentioned related issue number in PR description.
• [x] I have added screenshots and related demo links of my changes..
• [x] The title of my pull request is a short description of the requested changes.
• [x] My code follows the code style of this project.
• [x] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.
• [x] Open Source Program names(OPTIONAL: If you participated in any open-source program then please mention the program name here)