feat(fs): resolve content URIs on Android (#1658)

* Implemented writeTextFile on Android.

* Added license headers.

* fix fmt checks.

* implement more file APIs

* change file

* cleanup

* refactor dialog plugin to leverage new FS APIs

* implement metadata functions

* fix build

* expose FS rust API

* resolve resources on android

* update pnpm

* update docs

---------

Co-authored-by: Lucas Nogueira <lucas@tauri.app>

plugins/fs/src/desktop.rs

@@ -0,0 +1,35 @@
+// Copyright 2019-2023 Tauri Programme within The Commons Conservancy
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-License-Identifier: MIT
+
+use std::path::PathBuf;
+
+use tauri::{AppHandle, Runtime};
+
+use crate::{FilePath, OpenOptions};
+
+pub struct Fs<R: Runtime>(pub(crate) AppHandle<R>);
+
+fn path_or_err<P: Into<FilePath>>(p: P) -> std::io::Result<PathBuf> {
+    match p.into() {
+        FilePath::Path(p) => Ok(p),
+        FilePath::Url(u) if u.scheme() == "file" => u
+            .to_file_path()
+            .map_err(|_| std::io::Error::new(std::io::ErrorKind::InvalidInput, "invalid file URL")),
+        FilePath::Url(_) => Err(std::io::Error::new(
+            std::io::ErrorKind::InvalidInput,
+            "cannot use a URL to load files on desktop and iOS",
+        )),
+    }
+}
+
+impl<R: Runtime> Fs<R> {
+    pub fn open<P: Into<FilePath>>(
+        &self,
+        path: P,
+        opts: OpenOptions,
+    ) -> std::io::Result<std::fs::File> {
+        let path = path_or_err(path)?;
+        std::fs::OpenOptions::from(opts).open(path)
+    }
+}