docs: Adjust markdown link syntax in introduction.md

[peteness]

Adjust markdown link syntax in introduction.md

Checklist

• relevant documentation is changed or added
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

Notes: Updated markdown syntax to allow link anchoring for www addresses.

[welcome]

💖 Thanks for opening this pull request! 💖

We use semantic commit messages to streamline the release process. Before your pull request can be merged, you should update your pull request title to start with a semantic prefix.

Examples of commit messages with semantic prefixes:

• fix: don't overwrite prevent_default if default wasn't prevented
• feat: add app.isPackaged() method
• docs: app.isDefaultProtocolClient is now available on Linux

Things that will help get your PR across the finish line:

• Follow the JavaScript, C++, and Python coding style.
• Run npm run lint locally to catch formatting errors earlier.
• Document any user-facing changes you've made following the documentation styleguide.
• Include tests when adding/changing behavior.
• Include screenshots and animated GIFs whenever possible.

We get a lot of pull requests on this repo, so please be patient and we will get back to you as soon as we can.

[codebytere]

Thanks!

[welcome]

Congrats on merging your first pull request! 🎉🎉🎉

[release-clerk]

Release Notes Persisted

Updated markdown syntax to allow link anchoring for www addresses.

[trop]

I was unable to backport this PR to "11-x-y" cleanly;
you will need to perform this backport manually.

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I was unable to backport this PR to "12-x-y" cleanly;
you will need to perform this backport manually.

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I was unable to backport this PR to "13-x-y" cleanly;
you will need to perform this backport manually.

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I was unable to backport this PR to "14-x-y" cleanly;
you will need to perform this backport manually.