Loading en.json5 on Windows

[matthew-white]

We use a single .json5 file, src/locales/en.json5, which we load using json5-loader:

central-frontend/vue.config.js

Lines 14 to 19 in ea41488

	config.module
	.rule('json5')
	.test(/\/src\/locales\/en\.json5$/)
	.type('javascript/auto')
	.use('json5')
	.loader('json5-loader');

However, the regular expression uses / as the path separator, and it looks like that doesn't work on Windows: https://forum.getodk.org/t/setting-up-locally-odk-central-front-end-and-odk-central-back-end-for-development-on-windows-7/33364

We should be able to modify the regular expression to load en.json5 on Windows. The simplest thing might be to make the regular expression less specific by specifying something like /\.json5$/.