Added Sign up, Login and Logout funcionality

.idea/modules.xml

app/google-services.json

app/src/main/AndroidManifest.xml

app/src/main/java/com/example/taskboxx/Dashboard.java

app/src/main/java/com/example/taskboxx/LoginActivity.java

app/src/main/java/com/example/taskboxx/SignUpActivity.java

app/src/main/res/layout/activity_login.xml

app/src/main/res/layout/activity_sign_up.xml

app/src/main/res/menu/activity_dashboard_drawer.xml

app/src/main/res/values/styles.xml