Improve error handling

[humphd]

In https://github.com/tcvan0707/txt2html/blob/main/src/txt2html.js#L57-L61, I would improve things slightly:

// Move to its own function
function ensureDistDir() {
    try {
        await fs.mkdir(distDir);
    } catch {
        console.error(`Couldn't create ${distDir}, exiting`);
        process.exit(1);
    }
}

// later on call this...
ensureDistDir();

Here I log a helpful error message, don't print a call stack, and exit with an error code.