Declare 'extend' variable in docker.js

[gaberudy]

This 'extend' variable is not being defined which is causing errors in node v20.

[apocas]

https://github.com/apocas/dockerode/actions/runs/12610511590/job/35145175728

Not seeing any issues in Node 20.x tests, could you detail?

[gaberudy]

I'm not sure of why this isn't causing issues in the tests, but new to v4.0.3 our esbuild bundle of our server with dockerode won't start because of this missing "var" declaration.

I wonder if it was in a "," chain and then moved to it's own statement, but it's clearly an undefined variable. I am getting errors like:

/opt/backend/auth_server.cjs:135193
    extend = util2.extend;
           ^
ReferenceError: extend is not defined
    at ../../node_modules/dockerode/lib/docker.js (/opt/backend/auth_server.cjs:135193:12)

[apocas]

Yeah it's a typo, I missed the ";" before.
Just convert it into a ",", no need to segregate it.

Yeah this will not trigger everywhere.

[gaberudy]

@apocas Will you accept this PR now (replace ';' with ',')?