* added intro, item and prices video, fixed image links in item and prices
* update 2: first 5 videos added
* added all videos to the user manual
* updated .gitignore
* [enhance] Opening Invoice Tool create Opening Sales/Purchase Invoices
* [minor] added progress bar while creating invoice
* [minor] allow bulk upload for the invoices
* [minor] calculate item rate from net total
* [minor] added defaults for invoices fields, create gl entries only if grand_total is greater than 0
* [minor] check mandatory values before making opening invoices
* [minor] enable primary button if there is any error while creating invoices
* [minor] minor fixes, set company currency as invoice currency added tests
* [dashboard] added Opening Invoice Summery section in Dashboard
* [minor] added total invoices count on dashboard
* [minor] don't show dashboard if there are no opening invoices available
* [minor] added Opening Invoice Tools to Account's Tools section
* [minor] codecy fixes
* [fix] refactored general ledger and buttons on charts
* [fix] tests
