add bu-nav-start and bu-nav-end to add contents in navbar

[santoshyadavdev]

Is your feature request related to a problem? Please describe.
A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]

Describe the solution you'd like
A clear and concise description of what you want to happen.
add bu-nav-start and bu-nav-end to add contents in navbar
Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

I would be willing to submit a PR to fix this issue

[ ] Yes (Assistance is provided if you need help submitting a pull request)
[ ] No