Add documentation for Array.head

[ErikSchierboom]

Add documentation for the Array.head function.

Refs #184

[orcabot]

• docs/conceptual/collections.array-module-[fsharp].md - Article contains URLs. Make sure that non-Microsoft URLs are using the aka.ms shortener.
• docs/conceptual/array.head['t]-function-[fsharp].md - Article contains URLs. Make sure that non-Microsoft URLs are using the aka.ms shortener.

[orcabot]

Hi! I'm your friendly content validation bot. For this PR to be labeled as ready-to-merge, you'll need at least 2 comments from our designated community approvers containing the magic phrase LGTM (Looks good to me also works, for those of us that are really verbose).

@dend @KevinRansom @cartermp @thedanfernandez @dsyme - please validate this PR.

[dend]

⚠️ Validation status: warnings

File	Status	Preview URL	Details
docs/conceptual/collections.array-module-[fsharp].md	⚠️Warning		Details
docs/conceptual/array.head['t]-function-[fsharp].md	✅Succeeded

docs/conceptual/collections.array-module-[fsharp].md

• Line 42: [Warning] Invalid file link:(~/array.comparewith[&Add current F# release notes #39;t%5D-function-%5Bfsharp%5D.md).
• Line 44: [Warning] Invalid file link:(~/array.contains[&Add current F# release notes #39;t%5D-function-%5Bfsharp%5D.md).
• Line 46: [Warning] Invalid file link:(~/array.countby[&Add current F# release notes #39;t,&Add current F# release notes #39;key]-function-[fsharp].md).
• Line 48: [Warning] Invalid file link:(~/array.distinct[&Add current F# release notes #39;t%5D-function-%5Bfsharp%5D.md).

For more details, please refer to the build report.

Note: If you changed an existing file name or deleted a file, broken links in other files to the deleted or renamed file are listed only in the full build report.

[cartermp]

LGTM