docs: change license from MIT to CC BY-SA 4.0

LICENSE

@@ -1,21 +1,42 @@
-MIT License
+Creative Commons Attribution-ShareAlike 4.0 International
 
 Copyright (c) 2026 Ilia Sharin
 
-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:
+This work is licensed under the Creative Commons Attribution-ShareAlike 4.0
+International License. You should have received a copy of the license along with
+this work. If not, see https://creativecommons.org/licenses/by-sa/4.0/legalcode.
 
-The above copyright notice and this permission notice shall be included in all
-copies or substantial portions of the Software.
+To view a copy of this license, visit
+https://creativecommons.org/licenses/by-sa/4.0/ or send a letter to Creative
+Commons, PO Box 1866, Mountain View, CA 94042, USA.
 
-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.
+---
+
+You are free to:
+
+  Share — copy and redistribute the material in any medium or format
+  Adapt — remix, transform, and build upon the material for any purpose,
+          even commercially.
+
+Under the following terms:
+
+  Attribution — You must give appropriate credit, provide a link to the
+  license, and indicate if changes were made. You may do so in any reasonable
+  manner, but not in any way that suggests the licensor endorses you or your
+  use.
+
+  ShareAlike — If you remix, transform, or build upon the material, you must
+  distribute your contributions under the same license as the original.
+
+  No additional restrictions — You may not apply legal terms or technological
+  measures that legally restrict others from doing anything the license permits.
+
+Notices:
+
+  You do not have to comply with the license for elements of the material in
+  the public domain or where your use is permitted by an applicable exception
+  or limitation.
+
+  No warranties are given. The license may not give you all of the permissions
+  necessary for your intended use. For example, other rights such as publicity,
+  privacy, or moral rights may limit how you use the material.