Add new currency code SLE (925) for Sierra Leone

[rob-donovan]

As per ISO 4217 amendment 171:

The Sierra Leonean LEONE (SLL) is redenominated by removing three (3) zeros from the
denominations. A new currency code SLE/925 representing the new valuation
(1’000 times old SLL/694) is introduced on 1st April 2022 for any internal needs during the
redenomination process, and is replacing SLL as the official currency code, after the transition
period to be determined.
During this transition period, both the old Leone and new Leone will be in physical circulation
for at least 90 days.
The Bank of Sierra Leone will adopt the new code in the local system but SLL/694 shall
remain in use until further notice.
The Sierra Leonean currency shall continue to be the LEONE and this will not change
after redenomination.

https://www.six-group.com/dam/download/financial-information/data-center/iso-currrency/amendments/dl_currency_iso_amendment_171.pdf

[pykola]

Hello Team!
Could you please merge this PR?

[dprusakov]

@prasannjeet , @TakahikoKawasaki can I kindly ask you to merge this PR?🙏🏻

[prasannjeet]

@dprusakov Unfortunately I do not own this repo, and it seems like the owner no longer maintains it. I would suggest you to fork this repo, apply changes and use it.

[dprusakov]

@prasannjeet thanks a lot for highlighting that.

[totof3110]

@TakahikoKawasaki are you still maintaining this repo? If not would you be willing to grant other developers this role so development can continue? Thanks!