fix: miside cover image case

[Hythera]

The cover image of miside fails to load, as it has capitalized letters in the name, which are not the same as in src/assets/data/ecosystem.json. This might not be a problem on Windows, as it doesn't use case-sensitive file paths, but it is on Linux. Closes #2015

Error: ENOENT: no such file or directory, open '/nix/store/byikiv0256fvy3vra92pmfb0azla65zd-r2modman-3.2.11/share/r2modman/images/game_selection/miside.webp'
    at async open (node:internal/fs/promises:641:25)
    at async Object.readFile (node:internal/fs/promises:1245:14)
    at async file:///nix/store/byikiv0256fvy3vra92pmfb0azla65zd-r2modman-3.2.11/share/r2modman/electron-main.js:1:8635
    at async AsyncFunction.<anonymous> (node:electron/js2c/browser_init:2:53565) {
  errno: -2,
  code: 'ENOENT',
  syscall: 'open',
  path: '/nix/store/byikiv0256fvy3vra92pmfb0azla65zd-r2modman-3.2.11/share/r2modman/images/game_selection/miside.webp'

This PR basically just renames the MiSide.webp cover image to miside.webp to fix those issues.

[CLAassistant]

All committers have signed the CLA.