Added link from Targets to Platform Support in the book

[tgross35]

If you search the web for "rust targets", the first result is the targets page. However, usually when searching for this I'm interested in seeing the available triples with host information, so I just added a link to the correct page.

The entire Targets chapter could probably be combined into one page, since its three subchapters each only have a tiny section (I'll do this if requested)

[rustbot]

r? @GuillaumeGomez

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[tgross35]

@rustbot label +A-docs

[GuillaumeGomez]

r? rust-lang/libs

[JohnTitor]

Makes sense to me, thank you!

The entire Targets chapter could probably be combined into one page, since its three subchapters each only have a tiny section (I'll do this if requested)

The current looks great enough to me so I'm going to merge as-is.
@bors r+ rollup

[bors]

📌 Commit a582919 has been approved by JohnTitor

It is now in the queue for this repository.

[bors]

⌛ Testing commit a582919 with merge bb6e76d...

[tgross35]

Awesome, thanks!

[bors]

☀️ Test successful - checks-actions
Approved by: JohnTitor
Pushing bb6e76d to master...

[rust-timer]

Finished benchmarking commit (bb6e76d): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.9%	[-3.9%, -3.9%]	1
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

This benchmark run did not return any relevant results for this metric.

Cycles

This benchmark run did not return any relevant results for this metric.