Allow no BG color, update dependencies and config

[rafaucau]

resolves: #41

• [x] Update dependencies and config (flarum-cli audit infra --fix)
• [x] Allow no background color option

[iamdarkle]

Hey rafaucau great effort with this! I was just thinking about upgrading this extension to Webpack 5 and I came across your PR, I have built the js and have been testing it, so far so good.

I noticed that although now it allows you to leave the color blank, the meta theme-color tag that Flarum adds by default still overwrites and applies the main color of the forum, anyway that has nothing to do with this extension, I saw this thread about changing the theme-color https://discuss.flarum.org/d/20524-changing-the-meta-theme-color/ but I don't know if there is a way to remove it directly

[askvortsov1]

Thanks! Implementing most of these separately with some other changes