[WIP] .d.ts generator

[kdy1]

Steps for contribution

1. Clone dts branch of kdy1/swc

git clone [email protected]:kdy1/swc.git -b dts

2. Change directory

# From the swc directory
cd typescript/dts

3. Run cargo test twice

First run generates correct .d.ts files using tsc, and second run would actually invoke swc's type engine.
The first run will be very slow as it invokes tsc lots of time.

4. Modify typescript/checker

Validate valiidates the node T, while returning some extracted information.
Also, Validate may modify ast if it's required.

(Some ast nodes are modifiable only in validator. After inferencing type, it's not possible to modify as required)

5. Send PR to kdy1/swc with target branch 'dts'

[CLAassistant]

All committers have signed the CLA.