Fix typos and demo code in docs

[gin]

What changed? Why?

useWriteContract docs:

1. The tutorial useWriteContract() is using isPending instead of isLoading.
   Updated demo code to reflect this.

2. you'll'll should be you'll

3. Consistent codeblock MarkDown format where tsx: should be tsx

foundry setup docs:

4. forge build: should be forge build

oracles docs:

5. Chainlink's AggregatorV3Interface path is wrong. Updated path.
   https://docs.chain.link/data-feeds/using-data-feeds

Notes to reviewers
n/a

How has it been tested?
Visually.

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[cb-heimdall]

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[zencephalon]

Thank U for making these changes!