docs: add description of IBC to docs/ibc/overview.md

[barriebyron]

Description

now that Vega upgrade has passed and IBC is a standalone module, a clear definition of the IBC project is needed more than ever. This helpful plain language description helps visitors understand IBC.

It's funny that I haven't submitted this fix before since I get frustrated every time I visit the IBC Overview doc and don't find the answer to the heading question What is the Inter-Blockchain Communication Protocol (IBC)?

Let's add a description of IBC following that question

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Author Checklist

All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.

I have...

• included the correct type prefix in the PR title
• added ! to the type prefix if API or client breaking change
• targeted the correct branch (see PR Targeting)
• provided a link to the relevant issue or specification
• followed the guidelines for building modules
• included the necessary unit and integration tests
• added a changelog entry to CHANGELOG.md
• included comments for documenting Go code
• updated the relevant documentation or specification
• reviewed "Files changed" and left comments if necessary
• confirmed all CI checks have passed

Reviewers Checklist

All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.

I have...

• confirmed the correct type prefix in the PR title
• confirmed ! in the type prefix if API or client breaking change
• confirmed all author checklist items have been addressed
• reviewed state machine logic
• reviewed API design and naming
• reviewed documentation is accurate
• reviewed tests and test coverage
• manually tested (if applicable)

[amaury1093]

Nice addition

[barriebyron]

the "pre-provide-the-overview" page

not sure when the PR merge goes live, but I'll celebrate in advance. I'm glad to help reduce friction around understanding IBC

Happy holidays!