feat: add password field

[tlambert03]

closes #514 by adding a new widgets.Password

You can get a password widget, as usual, by specifying widget_type of 'Password'... but I also special cased arguments named "password" with an annotation of "str" that do not declare a widget_type.

both password and password2 will be Password widgets here:

@magicgui(password2={"widget_type": "Password"})
def login(username: str, password: str, password2: str):
    ...

[codecov]

Codecov Report

Base: 89.61% // Head: 89.63% // Increases project coverage by +0.02% 🎉

Coverage data is based on head (400de9f) compared to base (6a77140).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #515      +/-   ##
==========================================
+ Coverage   89.61%   89.63%   +0.02%     
==========================================
  Files          36       36              
  Lines        4353     4362       +9     
==========================================
+ Hits         3901     3910       +9     
  Misses        452      452              

Impacted Files	Coverage Δ
src/magicgui/backends/_ipynb/__init__.py	100.00% <ø> (ø)
src/magicgui/backends/_qtpy/__init__.py	100.00% <ø> (ø)
src/magicgui/types.py	87.17% <ø> (ø)
src/magicgui/widgets/__init__.py	100.00% <ø> (ø)
src/magicgui/widgets/bases/__init__.py	100.00% <ø> (ø)
src/magicgui/widgets/bases/_container_widget.py	91.66% <ø> (ø)
src/magicgui/backends/_ipynb/widgets.py	64.43% <100.00%> (+0.30%)	⬆️
src/magicgui/backends/_qtpy/widgets.py	88.28% <100.00%> (+0.05%)	⬆️
src/magicgui/widgets/_concrete.py	89.06% <100.00%> (+0.04%)	⬆️
src/magicgui/widgets/bases/_create_widget.py	97.50% <100.00%> (+0.06%)	⬆️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[haesleinhuepf]

Amazing. Thanks so much! 🎉