fix(plugin-inline-script-content): Ensure line numbers are correct when error is at line 1/2/3

[bengourley]

A bug with the logic adding the surrounding code to the stackframe meant that errors near the start of the document (line 1, 2 or 3) would result in negative-indexed surrounding code, e.g.:

  code: {
    '0': '  Error.apply(this, args)',
    '-2': '<!-- DOC START -->',
    '-1': '<script>function BadThing() {'
  }

This change fixes the logic so that the line numbers are correct and never go below 1.

[bugsnagbot]

@bugsnag/browser bundle size diff

	Minified	Minfied + Gzipped
Before	40.89 kB	12.24 kB
After	40.89 kB	12.24 kB
±	-2 bytes	-4 bytes

Generated by 🚫 dangerJS against 1c9fe96

[sazap10]

LGTM, works as expected after testing