Add repo mappings feature

[Yikun]

Currently, hub mirror action didn't have availablilty to sync the repos with different name, such as the requirement like #45 #64, the user want to sync github xxx.github.com repo to gitee repo xxx.

This patch adds the support for mappings, actually, accurately, it's the source repo mappings. The repo name will do the mapping covert according the mappings.

The compelete demo looks like:

- name: mirror with mappings
  uses: Yikun/hub-mirror-action@mappings
  with:
    src: github/yikun
    dst: gitee/yikunkero
    dst_key: ${{ secrets.GITEE_PRIVATE_KEY }}
    dst_token: ${{ secrets.GITEE_TOKEN }}
    mappings: "yikun.github.com=>blog"
    static_list: "yikun.github.com"

It will sync the github.com/yikun/yikun.github.com to gitee.com/yikunkero/blog

Closes: #45
Closes: #64