chore: add memory-fs to the devDependencies

[shogo82148]

It looks that ncc depends to memory-fs directly, but it is not in the dependencies.

ncc/src/index.js

Line 6 in c9238cc

const MemoryFS = require("memory-fs");

This pull request will fix a broken build in #921

[styfle]

You'll need to run yarn install so that it updates the yarn.lock file too

[shogo82148]

I did.
However yarn.lock is not updated, because memory-fs already exists in yarn.lock.

ncc/yarn.lock

Lines 10208 to 10214 in c9238cc

	memory-fs@^0.5.0:
	version "0.5.0"
	resolved "https://registry.yarnpkg.com/memory-fs/-/memory-fs-0.5.0.tgz#324c01288b88652966d161db77838720845a8e3c"
	integrity sha512-jA0rdU5KoQMC0e6ppoNRtpp6vjFq6+NY7r8hywnC7V+1Xj/MtHwGIbB1QaK/dunyjWteJzmkpd7ooeWg10T7GA==
	dependencies:
	errno "^0.1.3"
	readable-stream "^2.0.1"

$ yarn why memory-fs
yarn why v1.22.18
[1/4] 🤔  Why do we have the module "memory-fs"...?
[2/4] 🚚  Initialising dependency graph...
warning Resolution field "grpc@1.24.11" is incompatible with requested version "grpc@1.23.3"
[3/4] 🔍  Finding dependency...
[4/4] 🚡  Calculating file sizes...
=> Found "memory-fs@0.5.0"
info Has been hoisted to "memory-fs"
info Reasons this module exists
   - Specified in "devDependencies"
   - Hoisted from "ts-loader#enhanced-resolve#memory-fs"
info Disk size without dependencies: "52KB"
info Disk size with unique dependencies: "352KB"
info Disk size with transitive dependencies: "584KB"
info Number of shared dependencies: 9
✨  Done in 1.78s.

[styfle]

Thanks!