Update CHANGELOG.md

bump version tag to 2.1.0

Set version tag to 2.0.0

Update README.md

Update CHANGELOG.md

Merge pull request #25 from adtzlr/fix-r4-compatibility

Fix compatibility with default `real(kind=8)`

Merge branch 'main' of https://github.com/adtzlr/ttb into main

fix dot product of two vectors

fixes #14 : just a single loop over two vectors