docs: ✏️ Refer gcc 15.2

Author: maatthc

.gitignore

@@ -18,3 +18,4 @@ compile_commands.json
 # GCC
 avr_toolchain/
 avr_toolchain_build/
+avr-gcc-15.2.0-x64-linux/

.gitmodules

@@ -1,3 +1,6 @@
 [submodule "modules/jgandert"]
 	path = modules/jgandert
 	url = https://github.com/maatthc/jgandert_qmk_modules.git
+[submodule "modules/getreuer"]
+	path = modules/getreuer
+	url = https://github.com/getreuer/qmk-modules.git

README.md

@@ -64,8 +64,10 @@ export KEYBOARD="beekeeb/piantor"
 export KEYBOARD="crkbd/rev1"
 ```
 
-##### Compile with GCC v8.3.0
-Generates a firmware considerably smaller (~1.5k):
+##### Firmware size
+
+If you are facing issues with size, try different compiler versions: the v15.2 gives good results.
+Another possible options is to compile with GCC v8.3.0:
 
 ```
 ./install_avr_8.3.0.sh