fix(webpack): add missing process shim

[petermetz]

Describe the bug

The cockpit is crashing with

Uncaught ReferenceError: process is not defined

To Reproduce

1. build the project
2. start API server
3. launch cockpit in browser
4. observe the WSOD and the crash log on the console

Expected behavior

Cockpit does not crash.

Logs/Stack traces

Uncaught ReferenceError: process is not defined
    js cactus-common.web.umd.js:46764
    __webpack_require__ cactus-common.web.umd.js:72520
    js cactus-common.web.umd.js:46650
    __webpack_require__ cactus-common.web.umd.js:72520
    js cactus-common.web.umd.js:46632
    __webpack_require__ cactus-common.web.umd.js:72520
    js cactus-common.web.umd.js:24479
    __webpack_require__ cactus-common.web.umd.js:72520
    ts cactus-common.web.umd.js:72160
    __webpack_require__ cactus-common.web.umd.js:72520
    ts cactus-common.web.umd.js:72135
    __webpack_require__ cactus-common.web.umd.js:72520
    ts cactus-common.web.umd.js:71690
    __webpack_require__ cactus-common.web.umd.js:72520
    zZ7g cactus-common.web.umd.js:72555
    zZ7g cactus-common.web.umd.js:72556
    webpackUniversalModuleDefinition cactus-common.web.umd.js:3
    zZ7g cactus-common.web.umd.js:10
    Webpack 12
cactus-common.web.umd.js:46764
    js cactus-common.web.umd.js:46764
    __webpack_require__ cactus-common.web.umd.js:72520
    js cactus-common.web.umd.js:46650
    __webpack_require__ cactus-common.web.umd.js:72520
    js cactus-common.web.umd.js:46632
    __webpack_require__ cactus-common.web.umd.js:72520
    js cactus-common.web.umd.js:24479
    __webpack_require__ cactus-common.web.umd.js:72520
    ts cactus-common.web.umd.js:72160
    __webpack_require__ cactus-common.web.umd.js:72520
    ts cactus-common.web.umd.js:72135
    __webpack_require__ cactus-common.web.umd.js:72520
    ts cactus-common.web.umd.js:71690
    __webpack_require__ cactus-common.web.umd.js:72520
    zZ7g cactus-common.web.umd.js:72555
    zZ7g cactus-common.web.umd.js:72556
    webpackUniversalModuleDefinition cactus-common.web.umd.js:3
    zZ7g cactus-common.web.umd.js:10

Screenshots

Operating system name, version, build:

$ printf "$(uname -srm)\n$(cat /etc/os-release)\n"
Linux 5.4.0-56-generic x86_64
NAME="Ubuntu"
VERSION="20.04.1 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04.1 LTS"
VERSION_ID="20.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=focal
UBUNTU_CODENAME=focal

Hyperledger Cactus release version or commit (git rev-parse --short HEAD):

v0.2.0

Additional context

A little help with the fix itself: vfile/vfile#38 (comment)

cc: @sfuji822 @takeutak @jonathan-m-hamilton