Update README (#669)
Update README (#669)

* Rewrite README

* Update feature items style

* Fix typo

* Update wording

* format by grammarly

* Add links

* Add wiki link to README

* Add package development feature

Co-authored-by: Yuki Ueda <2b80720b0a7caa53a058edb0372b1cb65a262996@gmail.com>
Ikuyadeu/vscode-R,Ikuyadeu/vscode-R,Ikuyadeu/vscode-R