chore: initialize NexaCore compiler workspace with basic frontend and CLI

Add initial project structure for NexaCore programming language compiler:
- Create Cargo workspace with 4 crates (cli, driver, frontend, runtime)
- Add lexer with indentation-based tokenization and keyword support
- Add parser for modules, functions, structs, and basic expressions
- Implement CLI with build command and placeholder subcommands
- Add driver crate to orchestrate compilation pipeline
- Include .gitignore for Rust build

crates/nxc-cli/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "nxc-cli"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+authors.workspace = true
+
+[[bin]]
+name = "nexacore"
+path = "src/main.rs"
+
+[dependencies]
+nxc-driver = { path = "../nxc-driver" }
+