Remove grunt-rollup grunt plugin, replace with customRollup task,
config done via external rollup.config.js.

Remove uglify grunt plugin, replace with terser rollup plugin (does a
better job with source maps and chained minification)

Add nrcan-basemap grunt task for sibling project to get nrcan vector
tile basemap working with pmtiles.

Change the required structure of pmtilesRules.js - requires a sheet
that gets loaded via sheet.load(), after which all the style rules are
set and returned.  This allows style label rules to use IconSymbolizers,
however it requires a slightly awkward structure to be imposed on
a pmtiles stylesheet module.  See pmtilesRules.js, and corresponding
test stylesheet modules for more info.

Add await on loading the pmtilesRules.js stylesheet module

Add script 'test-serve' to package.json to run the test web server to debug test
HTML pages as required, removing the need to drop into a console

Update pmtiles test that was not testing rendering, only a blank map
canvas.

Add test mvt tiles to validate that protomapsL is available to stylesheet
modules upon import.

Add test for custom styled mvt data, with win32 capture only

Restructure test style modules to conform to new promise-returning
expected structure

Adjuust timeout limit on map-link whenReady()

Conditionally await on map-link.whenReady() for stylesheet module
associated to pmtiles / mvt layer (if omitted, don't want exceptions,
prefer to reject in whenReady(), although it's slow.

Add linux image for custom styles.  Loosen pixel comparison to 200 pixels

Remove postinstall --with-deps so that npm install does not require
root privilege