Moodle announced that support for IE would be dropped back in August
2020 with Moodle 3.9 but not active steps were taken at that time. That
decision was made in MDLSITE-6109 and this particular step was meant to
be taken in Moodle 3.10.
This is the first step taken to actively drop support for IE.
This commit also bumps the browser support pattern from 0.25% to 0.3%.
The percentage here includes any browser where at least this percentage
of users worldwide may be using a browser. In this case it causes
support for Android 4.3-4.4 to be dropped, which relate to Android
KitKat (released 2013).
This combination of changes means that all of the supported browsers in
our compatibility list support modern features including async,
for...of, classes, native Promises, and more which has a huge impact on
the ease of debugging code, and drastically reduces the minified file
size because a number of native Polyfills included by Babel are no
longer included.
Unfortunately the babel minify-mangle plugin seems to be abandoned and
in certain circumstances can be very buggy. The only safe options are to
disable it, or to switch to a different minification library.
Not minifying our javascript is not ideal, so this commit updates the
javascript tasks to use a rollup, combined with babel, and terser.
Babel still converts code from ES/UMD/AMD to AMD modules with the
relevant browser support, whilst terser minifies the code.
The rollup bundler handles tracking and creation of sourcemaps, and
supports better parallelisation of the tasks.
Since the upgrade to Node LTS/Gallium requires an upgrade to @babel/core
and eslint, which change the built files anyway, this seems like the
ideal time to make this change.
