Add support for customization with MUI theme to fields and delete buttons

[Madeorsk]

Problem

Some fields, inputs and buttons are not customizable by themes. This adds a way to set custom styles or props on all fields and on delete button.

Solution

Use styled components with a defined name in all fields and inputs.

Current limits:

• custom styles does not apply to empty fields

How To Test

make storybook

Then view a field, input or button you want to test with and try to change the default theme. For example:

export const defaultLightTheme: ThemeOptions = deepmerge(
    defaultThemeInvariants,
    {
        //...
        components: {
            //...

+           RaEmailField: {
+               styleOverrides: {
+                   root: {
+                       color: 'red',
+                   },
+               },
+           },
        },
    }
);

Additional Checks

• The PR targets master for a bugfix or a documentation fix, or next for a feature
• The PR includes unit tests (if not possible, describe why)
• The PR includes one or several stories (if not possible, describe why)
• The documentation is up to date

[djhi]

Great job otherwise!

[djhi]

Almost there!