Markdown linting: Hard tabs (MD010)

[dshevtsov]

Bug report

Description

The Markdown linter reports about 11725 issues when the rule 'MD010' is enabled.

Steps to reproduce

1. In the _checks/styles/style-rules-prod change exclude_rule 'MD010' to rule 'MD010'.
2. In your terminal, run rake test:md.

Test your updates

1. Follow "Steps to reproduce" locally to get list of errors to fix.
2. Preview the HTML locally to ensure your changes did not break formatting in the resulting HTML (run rake:preview). For more information, refer to the README.

Note-->Do NOT use special keywords in your commit message.

Expected result

All the reported issues are fixed.
The rake test:md command returns No issues found.

[shrielenee]

@danidelcar This will also have an impact on our repo.

[atwixfirster]

@dshevtsov ,

@danidelcar This will also have an impact on our repo.

Can we break this ISSUE into pieces?

For example, remove HARD TABS in B2B, Cloud, Coding Standards, etc...

Thank you!

[dshevtsov]

@atwixfirster feel free to create several PRs for different scopes like in #5252.