Fix not finding the theme menu when opening the project due to translation

[esthem]

Someone added Chinese language support before, and I found that it gave me an error when opening the project, so I fixed it and added some translation content.

in app/main-process/projectWindow.js

before

function ProjectWindow(filePath) {
    const getThemeFromMenu = () => Menu.getApplicationMenu().items.find(
        e => e.label.toLowerCase() === '&view'
    ).submenu.items.find(
        e => e.label.toLowerCase() === 'theme'
    ).submenu.items.find(
        e => e.checked
    ).label.toLowerCase();

after

function ProjectWindow(filePath) {
    const getThemeFromMenu = () => Menu.getApplicationMenu().items.find(
        e => e.label.toLowerCase() === i18n._('&View').toLowerCase()
    ).submenu.items.find(
        e => e.label.toLowerCase() === i18n._('Theme').toLowerCase()
    ).submenu.items.find(
        e => e.checked
    ).label.toLowerCase();

And added i18n support for some places, see code for details.