feat: add JS api

[hustcc]

from pyg2plot import Plot, JS

line = Plot("Line")
line.set_options({
  "height": 400, # set a default height in jupyter preview
  "data": [
    { "year": "1991", "value": 3 },
    { "year": "1992", "value": 4 },
    { "year": "1993", "value": 3.5 },
    { "year": "1994", "value": 5 },
    { "year": "1995", "value": 4.9 },
    { "year": "1996", "value": 6 },
    { "year": "1997", "value": 7 },
    { "year": "1998", "value": 9 },
    { "year": "1999", "value": 13 },
  ],
  "xField": "year",
  "yField": "value",
  "lineStye": JS('''function() {
    return { stroke: 'red' }; 
  }''')
})

[hustcc]

v0.1.8 done