Add simple justfile (#610)

Author: filmor

.formatter.exs

@@ -0,0 +1,3 @@
+[
+  subdirectories: ["rustler_tests", "rustler_mix"]
+]

justfile

@@ -0,0 +1,22 @@
+build:
+    cargo build
+    cd rustler_mix && mix deps.get && mix compile
+
+test:
+    cargo test -q
+    cd rustler_mix && mix deps.get && mix test
+    cd rustler_tests && mix deps.get && mix test
+
+test-all: test
+    cd rustler_mix && ./test.sh
+
+check-format:
+    cargo fmt --all -- --check
+    mix format --check-formatted
+
+format:
+    cargo fmt --all
+    mix format
+
+lint:
+    cargo clippy --all-targets --all-features