[17.0][IMP] account_statement_import_sheet_file: Improve readme

[florenciafrigieri2]

Improving readme. Adding context.

[OCA-git-bot]

Hi @alexey-pelykh,
some modules you are maintaining are being modified, check this out!

[etobella]

Thanks for the effort. Some small comments. Can you review them?

[etobella]

I would suggest

Business need
~~~~~~~~~~~~~

The same for all titles

[florenciafrigieri2]

Thanks for the idea! I'll take the suggestion to the functional group since the titles are not right now in the template, and we should change that first

[etobella]

Well, you should compare how it is seen in both cases:

Old:

New:

[yvaucher]

Appart from comments from @etobella LGTM

[florenciafrigieri2]

@etobella Can you solve the squash thing please?

[florenciafrigieri2]

@etobella Hello!! Can you please merge this :)?

[etobella]

@florenciafrigieri2 I am waiting for functional group's answer to my proposal of format. I made a small picture of how it is seen with both options and I made a commit in order to keep your original commit (in case the functional group wants to go back)

[vdewulf]

I answered to Flor and other people on our Discord channel, I like Enric's suggestion. I think it's easier to read.
Very nice new content in any case :)

[TumbaoJu]

I also like the use of headers to structure the file.