fix(plugin-tree): ship the MIT LICENSE the package.json files field already declares (#3647) (#3662)

`@object-ui/plugin-tree` lists "LICENSE" in package.json `files`, but
packages/plugin-tree/LICENSE did not exist. npm silently skips missing
`files` entries, so publish and CI both stayed green while every released
tarball shipped without the MIT text its own manifest promised — the only
one of 36 publishable packages in that state.

The added file is a byte-identical copy of the repository root LICENSE
(git blob cf2ca28), which is the exact
same blob all 35 sibling packages already carry.

Verified with `npm pack --dry-run` in packages/plugin-tree:
before 3 files (no LICENSE), after 4 files including 1.1kB LICENSE.


Claude-Session: https://claude.ai/code/session_01GTRjn8xBqp75dk7kFupVRt

Co-authored-by: Claude <noreply@anthropic.com>

Author: yinlianghui

packages/plugin-tree/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2024 ObjectQL
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.