Fix issue with html.replace mangling $&

This bug was discovered when using gulp-inline-source, which in turn uses inline-source

A JS file that looks as follows triggers the bug:
e&$&&(console.log("Hello world"));
    ^^ This $& is treated by html.replace as "Inserts the matched substring."
        Source:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/replace#Specifying_a_string_as_a_parameter

Note that '$&' can be generated by uglify-js (which is how I discovered the bug while using gulp-inline-source):
The original code was something like

      if (variable & mask) {
          doSomething()
      }

Uglify.js, automatically called from gulp-inline-source, which uses inline-source. optimized that code as follows:

      e&$&&(doSomething());

'variable' was shortened to 'e', 'mask' shortened to '$', and the 'if' replaced with '&&'.

As stated in the documentation linked to, the solution is to pass a function as replacement parameter, not a string.