Md2zhihu

- When using "--repo .xx" and xx has no remote configured, use the first found remote for pushing assets
- A wide table will produce tag `colgroup` inside a table that is not recognized by zhihu. `colgroup` is removed when building md table to html table.

refactor: default asset-branch: current_branch-md2zhihu-assets

refactor: add cli args and conf info to commit message when commit output_dir

feature: "--download" to download external image

feature: add md5 to asset fn to avoid conflict

- Fix help messages

fix: sort ref definition list and Reference list

fix: support unicode in link

- new-feature: support using "$" as math quote

Fixes

- fix: when output-dir is not asset-output-dir, it generates wrong url.

- fix: use the title to generate ref list text, instead of using link id. Make the ref-list more human friendly.

- fix: output ref-list and ref-def for only used links. Unused links will not appears on the bottom.

Features

- new-feature: add platform `minimal_mistake`: to convert md to `minimal_mistake` compatible version

- new-feature: add --rewrite to rewrite generate url, when one need to customize urls before uploading assets.

- new-feature: add arg "--jekyll" to respect jekyll syntax markdowns.

- new-feature: add option --refs to add external reference definition

Doc

- doc: fix readme: update according to latest changes