frontend: Set theme spacing

[septum]

Description

• Set the theme spacing
• Create and export a ThemeSpacing enum

Testing Performed

Manual testing

[jecr]

Just to get a clearer idea, how would this be used in the field?, does this replace the values the current theme.spacing outputs?

[septum]

Just to get a clearer idea, how would this be used in the field?, does this replace the values the current theme.spacing outputs?

Copy-pasting the example from above, it's expected to be used as the following examples:

<Grid
- spacing={2}
+ spacing={ThemeSpacing.Base}
>
  <Component />
 </Grid>

const StyledComponent = styled(Component)(({ theme }: { theme: Theme }) => ({
- margin: "24px",
+ margin: theme.spacing(ThemeSpacing.Medium),
}));