labels: mergeable

Fixes: #issue

Motivation and Context

Fix process is not defined error

Description

Eppo-exp/js-sdk-common#136 introduced a change to applicationLogger that added a check for process.env.LOG_LEVEL.
This doesn't work on the browser because process only exists in the Node environment.
Although there's a tricky reason why the original (process.env.NODE_ENV === 'production' ? 'warn' : 'info') expression didn't already fail, which is that webpack resolves the entire expression to simply warn since it resolves process.env.NODE_ENV to production at build time.
I've worked around it by doing a similar preprocessing step for LOG_LEVEL by adding a webpack.DefinePlugin to the webpack config that sets it to null.
This causes webpack to simplify the entire line to just level: "warn".

How has this been tested?

yarn webpack
Inspect the generated file dist/eppo-sdk.js. It should have a line line like below:

t.loggerPrefix = "[Eppo SDK]", t.logger = (0, n.default)({level: "warn", browser: {disabled: !0}})

Create a index.html file with the following contents:

<script src="file:///absolute/path/to/js-client-sdk/dist/eppo-sdk.js"></script>
<script>
    console.log(window.eppo);
</script>

Load this page in the browser and there should be no errors in the dev tools console.