Elements 2 doc release page

[jamesbradleym]

BACKGROUND:

• We're rolling out Elements updates that fundamentally change how curves are parameterized, we need to highlight these changes.

DESCRIPTION:

• Elements 2.0 Migration Doc w/ descriptions and code examples

TESTING:

• Take a look at the Elements_2.0.md file and learn Elements 2.0 changes that occurred!

FUTURE WORK:

REQUIRED:

• All changes are up to date in CHANGELOG.md.

COMMENTS:

• Any other notes.

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This change is 

[wynged]

not approving just so we can do the merge tomorrow not tonight

[wynged]

Reviewed 2 of 189 files at r1, 3 of 5 files at r2, 2 of 187 files at r3, 1 of 1 files at r4, all commit messages.
Reviewable status: 0 of 1 approvals obtained

[wynged]

Reviewed 185 of 187 files at r3.
Reviewable status: complete! 1 of 1 approvals obtained