chore: adding go.work and go.work.sum to gitignore

[damiannolan]

Description

I have recently started using a go.work file locally. It fixes an issue for me when using two go mods inside a single vscode workspace. Previously, opening any e2e files would show errors in vscode if the workspace is opened from the root of ibc-go. Adding a simple go.work file solves this.

There was some discussion about this in #1784 but we chose to not add it.
I propose that we follow what the sdk has done and add to .gitignore and provide a sample go.work file that people can chose to use locally if desired.

closes: #XXXX

Commit Message / Changelog Entry

chore: adding go.work to gitignore and providing example work file

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[crodriguezvega]

Nice, @damiannolan!