esbuild 0.13.9

Add support for imports in package.json (#1691)

This release adds basic support for the imports field in package.json. It behaves similarly to the exports field but only applies to import paths that start with #. The imports field provides a way for a package to remap its own internal imports for itself, while the exports field provides a way for a package to remap its external exports for other packages. This is useful because the imports field respects the currently-configured conditions which means that the import mapping can change at run-time. For example:
```
$ cat entry.mjs
import '#example'

$ cat package.json
{
  "imports": {
    "#example": {
      "foo": "./example.foo.mjs",
      "default": "./example.mjs"
    }
  }
}

$ cat example.foo.mjs
console.log('foo is enabled')

$ cat example.mjs
console.log('foo is disabled')

$ node entry.mjs
foo is disabled

$ node --conditions=foo entry.mjs
foo is enabled
```
Now that esbuild supports this feature too, import paths starting with # and any provided conditions will be respected when bundling:
```
$ esbuild --bundle entry.mjs | node
foo is disabled

$ esbuild --conditions=foo --bundle entry.mjs | node
foo is enabled
```
Fix using npm rebuild with the esbuild package (#1703)

Version 0.13.4 accidentally introduced a regression in the install script where running npm rebuild multiple times could fail after the second time. The install script creates a copy of the binary executable using link followed by rename. Using link creates a hard link which saves space on the file system, and rename is used for safety since it atomically replaces the destination.

However, the rename syscall has an edge case where it silently fails if the source and destination are both the same link. This meant that the install script would fail after being run twice in a row. With this release, the install script now deletes the source after calling rename in case it has silently failed, so this issue should now be fixed. It should now be safe to use npm rebuild with the esbuild package.
Fix invalid CSS minification of border-radius (#1702)

CSS minification does collapsing of border-radius related properties. For example:
```
/* Original CSS */
div {
  border-radius: 1px;
  border-top-left-radius: 5px;
}

/* Minified CSS */
div{border-radius:5px 1px 1px}
```
However, this only works for numeric tokens, not identifiers. For example:
```
/* Original CSS */
div {
  border-radius: 1px;
  border-top-left-radius: inherit;
}

/* Minified CSS */
div{border-radius:1px;border-top-left-radius:inherit}
```
Transforming this to div{border-radius:inherit 1px 1px}, as was done in previous releases of esbuild, is an invalid transformation and results in incorrect CSS. This release of esbuild fixes this CSS transformation bug.