docs: Updated building section to mention features

README.md

@@ -34,12 +34,22 @@ finished = true
 _Note: if event is not finished yet, it may have_ `end = start`.
 
 ## Building
-Requirements:  
+
+### Requirements
 - Rust toolchain
 - Slint dependencies (see [Platforms](https://docs.slint.dev/latest/docs/slint/guide/platforms/desktop/) and [Backends & Renderers](https://docs.slint.dev/latest/docs/slint/guide/backends-and-renderers/backends_and_renderers/))
 
-Instructions:  
-Just run `cargo build --release` and the resulting binary can be located at `target/release/aliveline[.exe]` if compilation succeeds.  
+### Feature flags
+By default Aliveline compiles with theme autodetection, provided by Slint, which sometimes does not work on Linux.  
+You can use these flags to compile Aliveline with selected theme:  
+- `light`
+- `dark`
+
+### Instructions
+Run `cargo build --release`  
+Pass features in build command with `-F foo` or `--feature foo`  
+Resulting binary will be located at `target/release/aliveline[.exe]`
+
 If compilation fails, double check that you have all required dependencies. If it still fails, file an issue on [Codeberg](https://codeberg.org/2ndbeam/aliveline/issues), including logs and system info.
 
 ## Usage