fix(fs): fix panic due to unwrap & truncate by default (#847)

* fix(fs): fix panic due to unwrap & truncate by default

closes #846

* fmt and change file

.changes/fs-create-new.md

@@ -0,0 +1,6 @@
+---
+"fs": "patch"
+"fs-js": "patch"
+---
+
+Add `createNew` option for `writeFile` and `writeTextFile` to create the file if doesn't exist and fail if it does.

.changes/fs-trunacte-non-append.md

@@ -0,0 +1,6 @@
+---
+"fs": "patch"
+"fs-js": "patch"
+---
+
+Truncate files when using `writeFile` and `writeTextFile` with `append: false`.

.changes/fs-write-panic.md

@@ -0,0 +1,6 @@
+---
+"fs": "patch"
+"fs-js": "patch"
+---
+
+Fix panic when using `writeFile` or `writeTextFile` without passing an option object.