add first UI mockup of main screen

Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "toolbox-tuner"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+relm4 = {version="0.4", features = ["libadwaita", "macros"]}
+
+[package.metadata.appimage]
+auto_link = true
+auto_link_exclude_list = [
+    "libc.so*",
+    "libdl.so*",
+    "libpthread.so*",
+]