Support specifying custom inline variable substitutions

[jbms]

🙋 feature request

Parcel supports inlining environment variables as process.env.XXXX string values but it does not seem to support inlining arbitrary value types (i.e. not just strings) as arbitrary dotted identifiers (i.e. not necessarily of the form process.env.XXXX).

This is supported by many other bundlers and also by swc: https://swc.rs/docs/configuration/compilation#jsctransformoptimizerglobals https://vitejs.dev/config/shared-options.html#define https://esbuild.github.io/api/#define https://webpack.js.org/plugins/define-plugin/

[github-actions[bot]]

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