feat: improve i18n support as a whole (#1526)

* feat: improve i18n support as a whole

- Remove dayjs in favor of /helpers/datetime.ts, which uses
Intl.DateTimeFormat and Date. Dayjs is not exactly i18n friendly
and has several locale related opened issues.

- Move/refactor date/time code from /helpers/utils.ts to
/helpers/datetime.ts.

- Fix Daily Review weekday not changing according to selected date.

- Localize Daily review weekday and month.

- Load i18n listed strings from /locales/{locale}.json in a dynamic way.
This makes much easier to add new locales, by just adding a properly
named json file and listing it only in /web/src/i18n.ts and
/api/user_setting.go.

- Fallback languages are now set in /web/src/i18n.ts.

- Full language codes are now preffered, but they fallback to 2-letter
codes when not available.

- The locale dropdown is now populated dynamically from the available
locales. Locale names are populated by the browser via
Intl.DisplayNames(locale).

- /web/src/i18n.ts now exports a type TLocale from availableLocales
array. This is used only by findNearestLanguageMatch(). As I was unable
to use this type in ".d.ts" files, I switched the Locale type from
/web/src/types/i18n.d.ts to string.

- Move pretty much all hardcoded text strings to i18n strings.

- Add pt-BR translation.

- Remove site.ts and move its content to a i18n string.

- Rename zh.json to zh-Hans.json to get the correct language name on
selector dropdown.

- Remove pt_BR.json and replace with pt-BR.json.

- Some minor layout spacing fixes to accommodate larger texts.

- Improve some error messages.

* Delete .yarnrc.yml

* Delete package-lock.json

* fix: 158:28  error  Insert `⏎`  prettier/prettier

api/user_setting.go

@@ -32,7 +32,25 @@ func (key UserSettingKey) String() string {
 }
 
 var (
-	UserSettingLocaleValue         = []string{"en", "zh", "vi", "fr", "nl", "sv", "de", "es", "uk", "ru", "it", "hant", "tr", "ko", "sl"}
+	UserSettingLocaleValue = []string{
+		"de",
+		"en",
+		"es",
+		"fr",
+		"it",
+		"ko",
+		"nl",
+		"pl",
+		"pt-BR",
+		"ru",
+		"sl",
+		"sv",
+		"tr",
+		"uk",
+		"vi",
+		"zh-Hans",
+		"zh-Hant",
+	}
 	UserSettingAppearanceValue     = []string{"system", "light", "dark"}
 	UserSettingMemoVisibilityValue = []Visibility{Private, Protected, Public}
 )