docs: add module import instructions for idiomorph extension

[jackielii]

Summary

• Added module import instructions to the idiomorph extension documentation
• Resolves confusion about the correct way to import idiomorph when using modules

Test plan

• Verified the import instruction matches the official idiomorph repository documentation
• Documentation renders correctly

Fixes #3349

🤖 Generated with Claude Code

[MichaelWest22]

It looks like your change is against a very old version of dev branch from a year ago. This is a documentation update ideally should be done to the latest master branch instead

[jackielii]

Hi @MichaelWest22 thanks for the review. Yes I realised that when I did the PR. The live docs at https://htmx.org/extensions/idiomorph/ is indeed very old. When I checkout dev, I found most instructions are up to date, that's why this PR is very small. But I still think it's worth adding this line because the right import for htmx is just idiomorph/htmx: it includes the idiomorph code as well as htmx extension part.

[jackielii]

OK, looking at it again. I realised the import "ideomorph" shouldn't be there, probably someone else updated it. I updated it with the right import path. Also ran formatting on it.

[jackielii]

sorry about the many commits, I cleaned up all the places where it mentions the js without htmx.

[1cg]

thank you @jackielii