docs: formula expansion as md sections

[dstala]

Change Summary

Provide summary of changes with issue number if any.

Change type

• feat: (new feature for the user, not a new feature for build script)
• fix: (bug fix for the user, not a fix to a build script)
• docs: (changes to the documentation)
• style: (formatting, missing semi colons, etc; no production code change)
• refactor: (refactoring production code, eg. renaming a variable)
• test: (adding missing tests, refactoring tests; no production code change)
• chore: (updating grunt tasks etc; no production code change)

Test/ Verification

Provide summary of changes.

Additional information / screenshots (optional)

Anything for maintainers to be made aware of

[wingkwong]

1. Suggest to use title case for the title. e.g. Conditional expressions -> Conditional Expressions
2. Heading of Related Articles is not aligned across these files. Numeric & String are using ### while Date & Conditional Expressions are using ##. With ###, it won't show in the sidebar.
3. For Conditional Expressions, it doesn't include This cheat sheet ....

[dstala]

1. Suggest to use title case for the title. e.g. Conditional expressions -> Conditional Expressions
2. Heading of Related Articles is not aligned across these files. Numeric & String are using ### while Date & Conditional Expressions are using ##. With ###, it won't show in the sidebar.
3. For Conditional Expressions, it doesn't include This cheat sheet ....

You have a big eye for details! Taken care!