chore: migration guide v2 to v3

changelog/v2_to_v3_migation.md

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+# Migration Guide - v2 to v3
+
+The `FtpServer` constructor has been changed to only take one object option. Combining the two just made sense.
+
+### From:
+
+```js
+const server = new FtpServer('ftp://0.0.0.0:21');
+```
+
+### To:
+
+```js
+const server = new FtpServer({
+  url: 'ftp://0.0.0.0:21'
+});
+```
+
+----
+
+The `pasv_range` option has been changed to separate integer variables: `pasv_min`, `pasv_max`.
+
+### From:
+
+```js
+const server = new FtpServer(..., {
+  pasv_range: '1000-2000'
+});
+```
+
+### To:
+
+```js
+const server = new FtpServer({
+  pasv_min: 1000,
+  pasv_max: 2000
+})
+```
+
+----
+
+The default passive port range has been changed to `1024` - `65535`
+
+----