NEPs repo Upgrade 2021-01

[arisac]

This issue describes the process NEPs repo will be upgraded and to use with the new NEPs website.

Step 1: Update current NEPs docs:

All changes for Upgrade in main branch from master branch

1. Move current NEPs files with new Directory Structure in 1 commit with:
   /NEPS/nep-$number.md -> /NEPS/nep-$number/index.md
2. Move current NEPs' auxiliary files with new Directory Structure in 1 commit with:
   /assets/nep-$number/* -> /NEPS/nep-$number/*
3. Remove /assets directory in 1 commit
4. Changing NEPs files with new Front Matter formatting in 1 commit
5. Update links in NEPs files in 1 commit
6. Update formatting with Common Mark Specs in 1 commit

Step 2: Initialize NEPs web site configs and files:

All changes for Upgrade in main branch from master branch

1. Add NewDocs Theme
2. Add NEPs Website Configs and custom codes
3. Add Github Actions for Format Check, Build Test and Deploy
4. Update README file and other necessary files
5. Deploy on test site

Step 3: Launch new NEPs Website

All changes in this step in pre-launch branch from main branch

1. Update Deploy script for official domain name and create a PR to main
2. Update DNS record
3. Update Gitbub NEPs default repo to main
4. Merge PR
5. Change Newton Project Website NEP link
6. Update README and NEP files in master branch with a notice for default branch changed and master branch is archived
7. All Done. Start using main branch and the website.