feat: add @vueuse/core and @vueuse/shared to Import Map

[keeplearning66]

Some demos in the document use @vueuse/core (e.g. Border-Radius), which leads to the error above and prevents the preview from being displayed.
So I added @vueuse/core and @vueuse/shared (since @vueuse/core depends on @vueuse/shared) to Import Map. I noticed that they also depend on vue-demi, but not adding vue-demi doesn't cause an error (I’m not sure why 🤔 ), so I haven’t added it for now.
I considered that only a few examples use @vueuse/core, and users probably won’t need to switch versions of @vueuse/core, so I didn't add it to Header.vue and set the version to latest.

[vercel]

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[Dsaquel]

My first though is that maybe we can try using workarounds and even delete the related code when it's not necessary like useElementSize.

There are only 5 occurrences of `vueuse` so i think it's feasible.

docs/examples/border/radius.vue:
  33  import { ref } from 'vue'
  34: import { useCssVar } from '@vueuse/core'
  35  

docs/examples/color-picker-panel/border.vue:
  21  import { computed, ref } from 'vue'
  22: import { useElementSize } from '@vueuse/core'
  23  

docs/examples/date-picker-panel/border.vue:
  24  import { computed, ref } from 'vue'
  25: import { useElementSize } from '@vueuse/core'
  26  

docs/examples/statistic/basic.vue:
  35  import { ref } from 'vue'
  36: import { useTransition } from '@vueuse/core'
  37  import { ChatLineRound, Male } from '@element-plus/icons-vue'

docs/examples/typography/convention.vue:
  28  <script lang="ts" setup>
  29: import { useCssVar } from '@vueuse/core'
  30  

[keeplearning66]

Thank you, I will try to modify these demos.