gulpfile.js

var gulp = require('gulp');
var sass = require('gulp-sass');
var livereload = require('gulp-livereload');
var inlineCss = require('gulp-inline-css');
var replace = require('gulp-replace');
var fs = require('fs');

sass.compiler = require('node-sass');
 
gulp.task('sass', function () {
    return gulp.src('./res/sass/*.scss')
        .pipe(sass().on('error', sass.logError))
        .pipe(gulp.dest('./res/build'))
        .pipe(livereload());
});
 
gulp.task('watch', function() {
    livereload.listen();
    gulp.watch('./res/sass/*.scss', gulp.series('build'));
    gulp.watch('./index.html', gulp.series('build'));
});  

gulp.task('inline', function() {
    return gulp.src('./*.html')
        .pipe(inlineCss({
            applyWidthAttributes: true,
            applyTableAttributes: true,
            removeHtmlSelectors: true,
            removeLinkTags: true
        }))
        .pipe(replace('%FONT-FACE%', function(s) {
            var tmpl = fs.readFileSync('font-face.html', 'utf8');
            return tmpl;
        }))     
        .pipe(gulp.dest('build/'));
});

gulp.task('default', gulp.series('watch'));
gulp.task('build', gulp.series('sass', 'inline'));