Add edamame.core + clojure.tools.reader.reader-types shim to core.janet.
init-edamame-shim! takes parse-string and read-form as args to avoid
circular module dependencies. Creates shim namespaces after SCI loads.
SCI eval-string is found and callable — next step is loading the 4
internal namespaces (interpreter, parser, analyzer, opts) whose source
files aren't loaded by the ns :require handler.