Fix bugs (swc-project#687)

- stript type-only export default
- allow `continue` in a for loop

Fix bugs (swc-project#683)

 - Fix block_scoping (Fix swc-project#682)
 - Handle new.target in susbscript position (Fix swc-project#675)

resolver: Handle method property correctly (swc-project#679)

Fix SourceMap (swc-project#672)

Previously, `SourceMap` (taken from rustc) has a bug which reuses start position when new_source_file is invoked concurrently.

Add { Load, Resolve }

Fix optimizer (swc-project#661)

Improve optimizer (swc-project#660)

Although it's quite naive at the moment, I added two optimization passes.

 - dead code elimination (Closes swc-project#607)
 - inlining

Unescape template literals before emitting. (swc-project#652)

Fixes swc-project#637.
Fixes swc-project#639.

Unescape template literals before emitting. (swc-project#652)

Fixes swc-project#637.
Fixes swc-project#639.

Remove empty expression in expression statement with top level await (s…

…wc-project#630)

Eats the semi-colon.

This doesn't compile (edit: doesn't compile the code in the tests) though because the target of that folder is ES2015. Also, this is kind of strange for me to put the tests in the "typescript" folder. Should we create something more general?

You can take over this PR if you'd like!