feat(ir): replace Rpl with GraphIr

Semi-broken as atm the CLI just does nothing except printing the parsed
IR, instead of actually executing it.

crates/ir/src/instruction/read.rs

@@ -0,0 +1,19 @@
+use serde::{Deserialize, Serialize};
+use std::path::PathBuf;
+
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
+pub struct Read {
+    pub source: SourceType,
+    pub format: SourceFormat,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
+pub enum SourceType {
+    File(PathBuf),
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
+pub enum SourceFormat {
+    Jpeg,
+    Png,
+}