Upgrade Tailwind to version 3

This pull request upgrades Tailwind to version 3 which also fixes the following error when installing dependencies:
    npm ERR! code ERESOLVE
    npm ERR! ERESOLVE could not resolve
    npm ERR!
    npm ERR! While resolving: postcss-load-config@3.1.4
    npm ERR! Found: postcss@7.0.39
    npm ERR! node_modules/postcss
    npm ERR!   dev postcss@"^7.0.35" from the root project
    npm ERR!   postcss@"^7" from @tailwindcss/postcss7-compat@2.2.17
    npm ERR!   node_modules/@tailwindcss/postcss7-compat
    npm ERR!     dev @tailwindcss/postcss7-compat@"^2.0.2" from the root project
    npm ERR!   40 more (autoprefixer, css-declaration-sorter, cssnano, ...)
    npm ERR!
    npm ERR! Could not resolve dependency:
    npm ERR! peerOptional postcss@">=8.0.9" from postcss-load-config@3.1.4
    npm ERR! node_modules/postcss-load-config
    npm ERR!   postcss-load-config@"^3.1.0" from @tailwindcss/postcss7-compat@2.2.17
    npm ERR!   node_modules/@tailwindcss/postcss7-compat
    npm ERR!     dev @tailwindcss/postcss7-compat@"^2.0.2" from the root project
    npm ERR!   peerOptional postcss-load-config@"^2.1.0 || ^3.0.0 || ^4.0.0" from svelte-preprocess@4.10.7
    npm ERR!   node_modules/svelte-preprocess
    npm ERR!     dev svelte-preprocess@"^4.6.1" from the root project
    npm ERR!   1 more (tailwindcss)
    npm ERR!
    npm ERR! Conflicting peer dependency: postcss@8.4.21
    npm ERR! node_modules/postcss
    npm ERR!   peerOptional postcss@">=8.0.9" from postcss-load-config@3.1.4
    npm ERR!   node_modules/postcss-load-config
    npm ERR!     postcss-load-config@"^3.1.0" from @tailwindcss/postcss7-compat@2.2.17
    npm ERR!     node_modules/@tailwindcss/postcss7-compat
    npm ERR!       dev @tailwindcss/postcss7-compat@"^2.0.2" from the root project
    npm ERR!     peerOptional postcss-load-config@"^2.1.0 || ^3.0.0 || ^4.0.0" from svelte-preprocess@4.10.7
    npm ERR!     node_modules/svelte-preprocess
    npm ERR!       dev svelte-preprocess@"^4.6.1" from the root project
    npm ERR!     1 more (tailwindcss)
    npm ERR!
    npm ERR! Fix the upstream dependency conflict, or retry
    npm ERR! this command with --force, or --legacy-peer-deps
    npm ERR! to accept an incorrect (and potentially broken) dependency resolution.
    npm ERR!
    npm ERR! See /Users/dave/.npm/eresolve-report.txt for a full report.

    npm ERR! A complete log of this run can be found in:
    npm ERR!     /Users/dave/.npm/_logs/2023-04-09T15_32_01_295Z-debug-0.log
matryer / xbar

Upgrade Tailwind to version 3 #884
