Adding export option to excel (.xlsx)

[Zvikan]

As https://github.com/devops-israel/aws-inventory/pull/21 is still on not completed, I took it into my hands and completed some parts of it.

• Downloading as an excel (.xlsx) and not TSV/VSC file
• Export per resource per region like #21
• Added export select-box at the bottom of the regions list panel
• Export by region (export everything in that region)
• Export everything (all regions)
• Empty tables(no resources under that region) will not be exported to avoid empty sheets

Notes: Exporting everything right now will download multiple files, excel files per region. The reasons I did it are:

• Excel sheet limited to 32 charts so can't have something like "us-west-2-cloudformation-x-y-z-a-b-c" and this required too much of substring or shorting the resource name which might create confusion to the user
• Single excel with all the available resources of all regions will have too many sheets and it will be tooooooooo long.. the user will get lost there, even if using the excel's "jump to a sheet by name option"

@kesor I am not sure if I am completely happy with the select-box position right now, let me know what do you think I can move it around or add some extra padding to prettier it

[Zvikan]

Added some top padding in the export div so it will have some spacing between the region navigation list to the export button line.