refactor: remove export handling from getExportPaths for wildcard matching

[devjiwonchoi]

Feature Explanation

The Wildcard Exports feature allows the user to set exports['./*'], and bunchee maps the wildcard with the Exportable Entries.

Requirements

The Exportable Entries a.k.a. exportables need to be inside the root src directory.

Exportable Entries

1. Files with allowed extension js | cjs | mjs | jsx | ts | tsx | cts | mts - excluding index (entry for ['.']).
2. Folders containing index file(s) with allowed extension.

Usage

Folder Structure:

- my-lib/
  |- src/
    |- a/
      |- index.ts
    |- b.ts
    |- index.ts
  |- package.json

package.json

{
  "name": "my-lib",
  "exports": {
    ".": {
      "types": "./dist/index.d.ts",
      "import": "./dist/index.js"
    },
    "./*": {
      "types": "./dist/*.d.ts",
      "import": "./dist/*.js"
    }
  }
}

Will be treated as:

{
  "name": "my-lib",
  "exports": {
    ".": {
      "types": "./dist/index.d.ts",
      "import": "./dist/index.js"
    },
    "./a": {
      "types": "./dist/a/index.d.ts",
      "import": "./dist/a/index.js"
    }
    "./b": {
      "types": "./dist/b.d.ts",
      "import": "./dist/b.js"
    }
  }
}

One design improvement could be: keep getExportPaths simple, that reciving a resolved exports map instead of cwd and doing cwd operation

Resolves: #243

[devjiwonchoi]

@huozhi Could you help me out on simplifying this code?

Objective

Return resolved exports by replacing resolved wildcard exports to the current './*'

Code

const resolvedExports = Object.assign(
  {},
  exports,
  ...resolvedWildcardExports, // typeof ExportCondition[]
  exports,
)
delete resolvedExports['./*']
return resolvedExports

[huozhi]

Great work! Thank you!!