chore(blog): simplify the blog js

Clean up the blog autosave JS and action

Refs #6368
chore(blog): replace save_draft.php with its js equivalent

Replaces save_draft.php with its js equivalent and reflects the changes in plugin init

Refs #6368
chore(blog): refactor auto save action and adds missing container references

Refactors the auto save action to be more readable, adds action description, adds container logic, removes unused variables

Refs #6368
chore(blog): correct syntax and combine jQuery selects

Corrects comparison operand, adds missing semincolon, combines jQuery operators, exposes update interval as a variable

Fixes #6368