Added custom metric for Webpack and ParcelJS

[kevinfarrugia]

Added custom metric to return array of known bundlers in use on a page.

Webpack

• https://webpagetest.httparchive.org/result/220529_JG_E/1/details/#waterfall_view_step1
• https://webpagetest.httparchive.org/result/220529_RD_C/1/details/#waterfall_view_step1

javascript_new	{"bundler":["webpack"]}

Parcel

• https://webpagetest.httparchive.org/result/220529_SW_J/1/details/#waterfall_view_step1

javascript_new	{"bundler":["parcel"]}

None

• https://webpagetest.httparchive.org/result/220529_FY_F/1/details/#waterfall_view_step1

javascript_new	{"bundler":[]}

Note that this implementation is built on wappalyzer's implementation and is only able to recognize Webpack and Parcel.