add ci

.gitlab-ci.yml

+image: "rust:latest"
+
+stages:
+  - lint
+  - build
+
+before_script:
+  - rustup target add thumbv6m-none-eabi
+  - rustup component add rustfmt
+  - rustup component add clippy
+  - cargo install flip-link
+  - cargo install elf2uf2-rs
+
+lint:
+  stage: lint
+  script:
+    - cargo fmt -- --check
+    - cargo clippy --all-features -- -D warnings
+
+build-rev3:
+  stage: build
+  script:
+    - cargo build --release
+    - elf2uf2-rs target/thumbv6m-none-eabi/release/cats-mobile-transceiver-mainboard firmware-rev3.uf2
+  artifacts:
+    paths:
+      - firmware-rev3
+
+build-rev2:
+  stage: build
+  script:
+    - sed -i "s/pub const REV_3_BOARD: bool = true;/pub const REV_3_BOARD: bool = false;/" companion-software/src/main.rs
+    - cargo build --release
+    - elf2uf2-rs target/thumbv6m-none-eabi/release/cats-mobile-transceiver-mainboard firmware-rev2.uf2
+  artifacts:
+    paths:
+      - firmware-rev2