feat: overwrite prev/next link (#61)

* feat: set Prev/Next to page data

* feat: set links at the bottom of page

* feat: hide next/prev links when themeConfig expressly set false

* feat: disable links when explicity set false

* feat: set customized link when explicity set

* fix: merge import from vitepress

src/client/theme-default/components/NextAndPrevLinks.ts

@@ -1,13 +1,42 @@
 import { defineComponent, computed } from 'vue'
-import { usePageData } from 'vitepress'
+import { usePageData, useSiteData } from 'vitepress'
 
 export default defineComponent({
   setup() {
     const pageData = usePageData()
+    const siteData = useSiteData()
+    const resolveLink = (targetLink: string) => {
+      let target: any = undefined
+      Object.keys(siteData.value.themeConfig.sidebar).some((k) => {
+        return siteData.value.themeConfig.sidebar[k].some(
+          (v: { children: any }) => {
+            if (Array.isArray(v.children)) {
+              target = v.children.find((value: any) => {
+                return value.link === targetLink
+              })
+            }
+            return !!target
+          }
+        )
+      })
+      return target
+    }
     const next = computed(() => {
+      if (pageData.value.frontmatter.next === false) {
+        return undefined
+      }
+      if (typeof pageData.value.frontmatter.next === 'string') {
+        return resolveLink(pageData.value.frontmatter.next)
+      }
       return pageData.value.next
     })
     const prev = computed(() => {
+      if (pageData.value.frontmatter.prev === false) {
+        return undefined
+      }
+      if (typeof pageData.value.frontmatter.prev === 'string') {
+        return resolveLink(pageData.value.frontmatter.prev)
+      }
       return pageData.value.prev
     })
     const hasLinks = computed(() => {