Is your feature request related to a problem? Please describe.
Sometimes, I'm on branch A and then I want to create and switch to a new branch based off of branch B. So I navigate to the B branch in the branches panel and press n. However, if I have changed files, this can present the git error where I must commit or stash my changes first. It's often the case that lazygit's autostash feature would have saved me but the functionality is not present in this flow.

I don't see a reason why not. The action is basically the same as checking out B in terms of moving the HEAD pointer and the autostash feature is present there. Whenever I run into this, I just press <space> instead which triggers the autostash push and pop, and then press n.

Describe the solution you'd like
When creating a new branch and git returns the commit or stash error, offer to autostash.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Reproduction:

git init
echo -e "a\n\nb" > file
git add .
git commit -m "add file"
echo -e "a\n\nc" > file
git add .
git commit -m "edit last line"
git checkout -b dev HEAD~
echo -e "b\n\nb" > file
lazygit

Checking out the other branch (<space>) will work but trying to create and switch to a new branch based off of it (n) will not.