fix: add node dev deps

[vasco-santos]

With the new aegir update, followed by merging #79 the build fails due to:

 > node_modules/mime-types/index.js:16:22: error: Could not resolve "path" (set platform to "node" when building for node)
    16 │ var extname = require('path').extname
       ╵                       ~~~~~~

 > node_modules/web-encoding/src/lib.cjs:4:61: error: Could not resolve "util" (set platform to "node" when building for node)
    4 │   typeof TextEncoder !== "undefined" ? TextEncoder : require("util").TextEncoder

This PR adds them as dev deps and adds the build to CI