Contents cache demo

[BUG] build.watch doesn't handle `~`

Hi, if I watch a file by this way:

build: {
        watch: [
            '~/.env',
        ]
    },

the build will not reload.

If I do:

build: {
        watch: [
            resolve(process.cwd(), '.env')
        ]
    },

it works!

I’ll maybe make a PR, if I have time to.

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