Add Dot Shape [DOTS] axis

### Requirements

By ticking the cases (or putting x between the square brackets in text mode), you confirm the following:

- [x] I have inspected the current [Axis Registry](https://github.com/googlefonts/axisregistry/tree/main/Lib/axisregistry/data) and there is not a registered custom axis that could be used for the variation purpose on the upcoming font project.
- [X] The metadata fields of the proposed axis meet the *Axis Requirements* as specified in the Protocol (linked above).

### Font project(s) using the axis

https://github.com/aminabedi68/Mikhak

### Short description of what the axis does

Transforms and/or switching dot style in precomposed glyphs

### Image

### Why is the axis needed

In Arabic, and possibly other scripts, dot styles contribute a lot to the appearance of a typeface. Traditional rombic dots (as written with a broad nib pen) give off a feeling of authoritativeness, while round dots or even several dots written cursively as either a line or a bent line or a loop communicate informality and a hand-written origin.

A font may implement several different dot styles that may be chosen at user discretion depending on design intent.

### Axis metadata fields

```
#DSTY based on [Mikhak](https://github.com/aminabedi68/Mikhak)
tag: "DSTY"
display_name: "Dot Style"
min_value: 1
default_value: 1
max_value: 1000
precision: 1
fallback {
name: "Default"
value: 1.00
}
fallback_only: false
description: ""
````

Note: _I'm not sure what `fallback_only` means and it wasn't described in the Guide, so leaving it at default value._