Combining three polygons and contour the edges

[Swaroopa-Agribridge]

I am working on RNMapBox And Now I Have 3 polygons which are adjacent to each other

polygons =

[
[
[78.36999594594597, 17.736575959425156],
[78.37002594594598, 17.736575959425156],
[78.37002594594598, 17.73660595942516],
[78.36999594594597, 17.73660595942516],
[78.36999594594597, 17.736575959425156],
],
[
[78.37002394150257, 17.736575959425156],
[78.37005394150258, 17.736575959425156],
[78.37005394150258, 17.73660595942516],
[78.37002394150257, 17.73660595942516],
[78.37002394150257, 17.736575959425156],
],
[
[78.36999594594597, 17.73654801721783],
[78.37002594594598, 17.73654801721783],
[78.37002594594598, 17.736578017217834],
[78.36999594594597, 17.736578017217834],
[78.36999594594597, 17.73654801721783],
],
];
Now I want to combine these polygons and contour the outer edges of the polygon and show as single polygon

I used convex hull , concave hull turf also but at the L shape I am getting the diagonal shape. whatever the shape is I want to contour the all the outer edges of the polygons and here my polygons are dynamically created.

Can anyone tell me how to do it.