CRAN Release 2.1.0

[brownag]

• Fix URLs for Winbuilder (https://win-builder.r-project.org/3TJ5CRF2wBCN/00check.log)

Found the following (possibly) invalid URLs:
  URL: https://binder.pangeo.io/v2/gh/giswqs/whitebox-r-binder/master?urlpath=rstudio
    From: README.md
    Status: Error
    Message: Failed to connect to binder.pangeo.io port 443: Timed out
  URL: https://codecov.io/gh/giswqs/whiteboxR (moved to https://app.codecov.io/gh/giswqs/whiteboxR)
    From: README.md
    Status: 200
    Message: OK

• Update demo.Rmd
• R Hub Check --as-cran
• Local R CMD Check
• devtools::spell_check() / update WORDLIST
• News (no 2.1.0 release on jblindsay/whitebox-tools)

[giswqs]

Thanks for fixing this. The Pangeo binder has been discontinued by Pangeo before it was abused by crypto miners.