[ARROW-11175] [R] Small docs fixes

• Type: New Feature
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 3.0.0
• Component/s: R
• Labels: pull-request-available
• Assignee: Jonathan Keane
• Reporter: Jonathan Keane
• Created: 07/Jan/21 21:59
• Updated: 13/Jan/21 20:06
• Resolved: 13/Jan/21 20:05

Description

• shell {{}} is missing on the first line
• On https://arrow.apache.org/docs/r/reference/write_to_raw.html, the link to write_ipc_stream() is broken
• the source links on pkgdown need a subdir (this might need a pkgdown fix)
• the example cmake command on README.md needs a linebreak slash on the first line

Issue Links

• links to: GitHub Pull Request #9196