Keyboard shortcut for the blame button
### Problem to solve
As a new maintainer of a project, I want a fast way to find a file and see why a certain line was added.
### Intended users
* [Delaney (Development Team Lead)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#delaney-development-team-lead)
* [Sasha (Software Developer)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#sasha-software-developer)
* [Sam (Security Analyst)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#sam-security-analyst)
* [Simone (Software Engineer in Test)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#simone-software-engineer-in-test)
### Further details
I prefer mouseless workflow if possible.
### Proposal
Add <kbd>b</kbd> keyboard shortcut to file view.
issue