New Flex component

[marcialfps]

Changes

• New Flex component. Closes Implement Flex component #1209
• Remove DxcStack from List and QuickNav components.
• Remove DxcStack from stories.

[GomezIvann]

I think we are missing some key props from Flexbox, here is a summary of them:

1. flex-grow as grow.
2. flex-basis as basis.
3. flex-shrink as shrink.
4. align-self stays the same.

[marcialfps]

I think we are missing some key props from Flexbox, here is a summary of them:

1. flex-grow as grow.
2. flex-basis as basis.
3. flex-shrink as shrink.
4. align-self stays the same.

These props are applied to each child, not to the container.

[GomezIvann]

I think we are missing some key props from Flexbox, here is a summary of them:

1. flex-grow as grow.
2. flex-basis as basis.
3. flex-shrink as shrink.
4. align-self stays the same.

These props are applied to each child, not to the container.

Flex can be both container and/or contained item. Here is an example with grow prop:

      <DxcFlex>
        <DxcFlex grow={0}>
          <DxcTextInput label="First name" size="fillParent" />
        </DxcFlex>
        <DxcFlex grow={0}>
          <DxcTextInput label="Second name" size="fillParent" />
        </DxcFlex>
        <DxcFlex grow={1}>
          <DxcTextInput label="Location" size="fillParent" />
        </DxcFlex>
      </DxcFlex>