docs(explorer): Add changelog entry

[brunomenezes]

Summary

Add changelog information for the next explorer release v3.5.0.

PS: This PR I am merging this without waiting for any approval since it is just Changelog updates for release

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Name	Status	Preview	Updated (UTC)
rollups	✅ Ready (Inspect)	Visit Preview	Jun 26, 2023 1:48am
staking	🔄 Building (Inspect)		Jun 26, 2023 1:48am

[coveralls]

Pull Request Test Coverage Report for Build 5372963784

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 72.752%

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Totals
Change from base Build 5372582201:	0.0%
Covered Lines:	2548
Relevant Lines:	3337

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💛 - Coveralls