Add SpeckDL compiler scaffold

- CLI entry point with yargs parsing for speckl-compile <file> --output-dir --bom-format
- TypeScript parser with AST types for all SpeckDL primitives
- Generator for PROV-O JSON-LD provenance graphs
- Generator for CycloneDX v1.6 BOMs
- Generator for SPDX 3.0.1 BOMs
- E2E test verifying RetryHandler.speck parsing and all output formats

All tests pass.

compiler/node_modules/postcss/lib/stringify.d.ts

@@ -0,0 +1,9 @@
+import { Stringifier } from './postcss.js'
+
+interface Stringify extends Stringifier {
+  default: Stringify
+}
+
+declare let stringify: Stringify
+
+export = stringify