Clean up types of numbers in the position interface

[DominicOram]

As someone using cs-web-lib in my app it's confusing that parameters that I would naturally expect to be numbers are expected to be passed in as strings e.g. many of the items in

cs-web-lib/src/types/position.ts

Line 8 in b307d18

export interface Position {

. See initial confusion at DiamondLightSource/atlas#84 (comment).

Acceptance Criteria

• We can pass these values in as numbers
• If we must keep backwards compatibility we still allow strings but ideally I feel like they should be typed as just numbers

[abigailalexander]

Thanks for pointing this out! I'll create a ticket in our JIRA to look into this. Most likely we'll still allow strings, as this allows us to pass dimensions in as percentages too, but passing pixel sizes directly in as numbers as well seems sensible.