Adjust formatting of accessibility guide link in Edit file and Pipeline editor

Context

From !193026 (merged):

The pipeline editor uses Monaco text editor. Monaco has some great a11y features built in, including a mechanism for escaping keyboard traps.

The user is not made aware that it uses the Monaco text editor, so is not aware of the a11y features. This can lead to a user becoming keyboard trapped using the tab key.

!193026 (merged) added an Editor accessibility guide link to the Pipeline Editor. !218605 (merged) added an Editor accessibility guide link to the Source Code Edit single file view.

Other related issues:

• Fix soft wrap not working due to accessibilityS... (!217065 - merged)
• Soft-Wrap in single file edit mode is not worki... (#524739 - closed)

Design proposal

The formatting and UX of this link could be improved.

1. Make the link open in a new tab, so users don't lose context or work while they are editing a file / pipeline.
2. Adjust the layout. Coordination with Pipelines designers needed. See #585923 (comment 3003707286).