slip-0044.md misses currency abbreviations

[morriswinkler]

The List: Registered coin types within slip-0044.md is missing the currency abbreviations lice BTX ETH XRP ... and so on.

[prusnak]

Feel free to open the pull request adding the abbreviations. Thank you! Creating a new column for abbreviations and moving existing abbreviations from coin name to this column would be the best! 👍

[morriswinkler]

I like to ref issues within my PR's and close them when they are done. But nevertheless, i already started on a PR.

@prusnak I figured that most people use the word symbol instead of abbreviation, any objections?

[prusnak]

What is word symbol?

[prusnak]

Ah, I get it. You mean the word "symbol", not "the word symbol". Ok, no objections.