docs(elements): add angular element term to glossary

[jbogarthyde]

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[ ] Bugfix
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Other information

[mary-poppins]

You can preview 69440b8 at https://pr23807-69440b8.ngbuilds.io/.

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[IgorMinar]

I just realized that we have previously capitalized E in Elements. Was that wrong? Or should we update this with capital E?

[IgorMinar]

resolved in person - it should be lower case e

[IgorMinar]

resolved in person - it should be lower case e

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