feat: standalone bundler

src/fs/README.md

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+# nexe-fs
+
+This module contains a set of patches used to create (and use) the nexe virtual filesystem
+
+---
+
+### Getting Started:
+
+To patch the module loader, monkey patches must be installed on a few methods at the time that node boots up. This requires a special build of node. Nexe provides these builds or the patch can be applied from this module manually in your own build setup.
+
+```javascript
+const bootstrapPatch = fs.readFileSync(require.resolve('nexe-fs/bootstrap'), 'utf-8')
+// insert boostrapPatch wherever node starts up. For reference, Nexe does this
+// in third-party-main.ts
+```
+
+To create a virtual file system use the `Bundle` Object
+
+```javascript
+const { Bundle } = require('nexe-fs')
+
+const bundle = new Bundle({ cwd })
+await bundle.addResource(absoluteFileName)
+
+bundle.toStream().pipe(fs.createWriteStream('./myFsBlob'))
+
+// You'll also want to save the bundle index to use at runtime
+// It can be saved by accessing bundle.index (object/hash) or serializing the bundle with JSON.stringify(bundle)
+```
+
+In the entrypoint of the custom node build, the fs patch needs to be applied
+```javascript
+const fakeFs = fs.readFileSync(require.resolve('nexe-fs/patch'), 'utf-8')
+//apply this code to your entrypoint
+```
+
+The patch exposes two methods, `shimFs` and `restoreFs` to be used as follows:
+
+```javascript
+shimFs({
+  blobPath: 'location/of/myFsBlob',
+  resources: bundle.index,
+  layout: {
+    stat: blobStats //fs.Stats object about the blob at blobPath
+    resourceStart: 0 // the offset within the blob that is referenced by the bundle index
+  }
+})
+```
+
+At this point executing the original entrypoint shoudl result in usage of the virtual filesystem.
+
+
+