add note about squashing commits

add note about type casting in flow

add note about git checkout -b

note about git filter-branch

fix conflict

add file about VSCode shortcut

add note about keybaord shortcuts panel

add note about git gc

add note about css descendant combinator

small change in SOLID note

start adding note on SOLID principles

fix path data structures notes

fix path

add note about Docker

add details to CSS specificity