feat(dates): allow multiple values for defaultDateType config

Allows the user to set fallback values for the `defaultDateType` setting

Prior to this commit, if the date was not set, it would default to the
current time. e.g. if using `defaultDateType == "published"` or if
the CreatedModifiedDate plugin's `priority` setting is set without
`filesystem`

docs/configuration.md

@@ -40,6 +40,7 @@ This part of the configuration concerns anything that can affect the whole site.
   - Note that Quartz 4 will avoid using this as much as possible and use relative URLs whenever it can to make sure your site works no matter _where_ you end up actually deploying it.
 - `ignorePatterns`: a list of [glob](<https://en.wikipedia.org/wiki/Glob_(programming)>) patterns that Quartz should ignore and not search through when looking for files inside the `content` folder. See [[private pages]] for more details.
 - `defaultDateType`: whether to use created, modified, or published as the default date to display on pages and page listings.
+  - Can be a list (e.g. `["created", "modified"]`) to define fallbacks (highest priority first).
 - `theme`: configure how the site looks.
   - `cdnCaching`: If `true` (default), use Google CDN to cache the fonts. This will generally will be faster. Disable (`false`) this if you want Quartz to download the fonts to be self-contained.
   - `typography`: what fonts to use. Any font available on [Google Fonts](https://fonts.google.com/) works here.

quartz/cfg.ts

@@ -56,7 +56,7 @@ export interface GlobalConfiguration {
   /** Glob patterns to not search */
   ignorePatterns: string[]
   /** Whether to use created, modified, or published as the default type of date */
-  defaultDateType: ValidDateType
+  defaultDateType: ValidDateType | ValidDateType[]
   /** Base URL to use for CNAME files, sitemaps, and RSS feeds that require an absolute URL.
    *   Quartz will avoid using this as much as possible and use relative URLs most of the time
    */

quartz/components/Date.tsx

@@ -16,7 +16,8 @@ export function getDate(cfg: GlobalConfiguration, data: QuartzPluginData): DateT
       `Field 'defaultDateType' was not set in the configuration object of quartz.config.ts. See https://quartz.jzhao.xyz/configuration#general-configuration for more details.`,
     )
   }
-  return data.dates?.[cfg.defaultDateType]
+  const types = cfg.defaultDateType instanceof Array ? cfg.defaultDateType : [cfg.defaultDateType]
+  return types.map((p) => data.dates?.[p]).find((p) => p != null)
 }
 
 export function formatDate(d: DateTime, locale: ValidLocale = "en-US"): string {