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.js

@@ -0,0 +1,11 @@
+'use strict'
+
+let Stringifier = require('./stringifier')
+
+function stringify(node, builder) {
+  let str = new Stringifier(builder)
+  str.stringify(node)
+}
+
+module.exports = stringify
+stringify.default = stringify