Merge pull request #26 from soluble-io/travis-php8

ci(travis): back to bionic and try "8.0"

ci(travis): dist to focal

chore(mkdocs): updated to 6.2

ci(travis): ignore platform reqs for php8

ci: php8 in travis matrix

Merge pull request #25 from soluble-io/php8

fix travis php7.1 with composer 2.0

reorder dev dependencies

update to mkdocs material 6.1

fix travis for php7.1

fix travis for php7.1

fix travis for php7.1

fix travis for php7.1

docs: pre release 2.2.0