feat: add omnivores cookbook

[wengtad]

Added one of the website on #489 .

Facing an issue during committing the code to git causing by flake8.

git -c user.useConfigOnly=true commit --quiet --allow-empty-message --file - 
check yaml...........................................(no files to check)Skipped
fix end of files.........................................................Passed
trim trailing whitespace.................................................Passed
flake8...................................................................Failed
- hook id: flake8
- exit code: 1

tests/test_omnivorescookbook.py:64:13: FS003 f-string missing prefix

isort....................................................................Passed
black....................................................................Passed

The code on the test_omnivorescookbook.py:64 is the recipe description shown as below:

A super quick and easy stir fried bok choy with tofu puffs that only uses five ingredients and takes 15 minutes to prep and cook. The crisp bok choy is lightly caramelized and combined with tender tofu in a savory and slightly sweet sauce. It is surprisingly satisfying to eat as a side dish, and sometimes I serve it as a light main dish for lunch over steamed rice. {Vegan, Gluten-Free Adaptable}To make the dish gluten-free, use tamari to replace light soy sauce.

To temporary make it success to commit to git, I had change the .flake8 file. Will need help on this part.