Add explanation mark on tab title when there is new interactive argument

[mmalczak]

ARTIQ Pull Request

Description of Changes

Add explanation mark on tab title when there is new interactive argument.
Ideal solution would be to bold 'Interactive arguments' tab title to notify about new argument, but I did not find direct way to do it. I add explanation mark instead.

Type of Changes

	Type
✓	✨ New feature

Steps (Choose relevant, delete irrelevant before submitting)

All Pull Requests

• Use correct spelling and grammar.
• Check the copyright situation of your changes and sign off your patches (git commit --signoff, see copyright).

Code Changes

• Run flake8 to check code style (follow PEP-8 style). flake8 has issues with parsing Migen/gateware code, ignore as necessary.
• Test your changes or have someone test them. Mention what was tested and how.
• Add and check docstrings and comments
• Check, test, and update the unittests in /artiq/test/ or gateware simulations in /artiq/gateware/test

Documentation Changes

Licensing

See copyright & licensing for more info.
ARTIQ files that do not contain a license header are copyrighted by M-Labs Limited and are licensed under LGPLv3+.