Run keycloakify behind corporate proxy

Fixes #257

Use make-fetch-happen for the download step. This lib will use `PROXY`
and `HTTPS_PROXY` and `NO_PROXY` env vars out of the box.

Additionally we'll try and get proxy config from npm. Unfortunately,
the most straightforward options is to call npm config to do this, since
npm  config is not easily extracted as a lib and we don't want to
replicate the resolution mechanisms.

package.json

@@ -62,6 +62,7 @@
     },
     "devDependencies": {
         "@babel/core": "^7.0.0",
+        "@types/make-fetch-happen": "^10.0.1",
         "@types/memoizee": "^0.4.7",
         "@types/minimist": "^1.2.2",
         "@types/node": "^18.14.1",
@@ -73,15 +74,16 @@
         "properties-parser": "^0.3.1",
         "react": "18.1.0",
         "rimraf": "^3.0.2",
-        "typescript": "^4.9.5",
+        "scripting-tools": "^0.19.13",
         "ts-node": "^10.9.1",
-        "scripting-tools": "^0.19.13"
+        "typescript": "^4.9.5"
     },
     "dependencies": {
         "@octokit/rest": "^18.12.0",
         "cheerio": "^1.0.0-rc.5",
         "cli-select": "^1.1.2",
         "evt": "^2.4.15",
+        "make-fetch-happen": "^11.0.3",
         "minimal-polyfills": "^2.2.2",
         "minimist": "^1.2.6",
         "path-browserify": "^1.0.1",