add logos and logo license (#3739)

## Change
- Added LOGO_LICENSE.md in the root
- Added the std logo and the transparent version under docs/

## General checklist
- [V ] There are no breaking changes (API, behaviour)

---------

Co-authored-by: Dmytro Liubarskyi <ljubarskij@gmail.com>

LOGO_LICENSE.md

@@ -0,0 +1,26 @@
+# LangChain4j Logo License
+
+The LangChain4j logo (a cup of coffee with a parrot next to it) is a trademark of the LangChain4j project.
+
+We want the community to freely use the logo in ways that support adoption,
+learning, and discussion of LangChain4j.
+
+At the same time, we need to protect the project’s identity
+and avoid confusion about what is or isn’t officially part of LangChain4j.
+
+## Permitted Uses
+
+You may use the logo without additional permission in the following contexts:
+
+- Books, tutorials, talks, videos, courses, and other educational content about LangChain4j.
+- Articles, blog posts, and presentations discussing or teaching LangChain4j.
+- Community events, meetups, and hackathons.
+- Informational graphics, blog headers, or social media posts referencing LangChain4j.
+
+No attribution is required, though mentioning the LangChain4j project is appreciated.
+
+## Requesting Exceptions
+
+If you would like to use the logo in a way not covered above,
+please open an issue in the LangChain4j GitHub repository
+or contact the maintainers through community channels to request permission.