Transaction Metadata overview: Correct ranges of 64bit integers

[bjornkihlberg]

Checklist

• I have read the How to Contribute.
• I have run yarn build after adding my changes without getting any errors.
  No, I'm only changing the readme.

Updating documentation or Bugfix

Correct ranges of 64bit signed and unsigned integers.

I'm assuming it should be a 64bit integer, in which case the ranges are currently incorrect. Here's a stackoverflow thread with an answer with 87 upvotes strengthening my argument if you don't believe me.

[rphair]

The range after Integers in the range is obviously impossible with a 64-bit value... but I think we need a definitive reference or schema saying whether this value is signed or unsigned.

That section, even after your change, implies the integer metadata is a signed value... while the earlier text "between 0 and ..." for your first change suggests that it is unsigned. This was also a problem with the original text and therefore also indicates a need to reference the source material in this PR and probably also the document itself.

[os11k]

Thank you for your PR! I would like to add, even if you "only changing the readme" it is mandatory to run yarn build, that why it is in a checklist. Stackoverflow is nice source of information, but more hard evidences would be necessary, imho.