Add snippets for julia and delete pi and phi

[benneti]

Removing phi and pi as it can cause conflicts and problems in julia and latex modes (also in org-mode) and other programming modes, see #39.
Also add snippets for julia-mode, some snippets where taken from https://github.com/AndreaCrotti/yasnippet-snippets, I left the contributors name in these snippet files.

[benneti]

implemented the requested changes. Before you merge could you tell me what this implicit selection does? I did not find it https://joaotavora.github.io/yasnippet/snippet-development.html nor by a quick search in doom emacs.
Also I am not completely sure how YASnippet works so would it be better to insert blocks such that $0 is after the block or like how I did it right now?

[hlissner]

Quoting the relevant section of yasnippet's docs

From version 0.6, snippets expansions are run with some special Emacs-lisp variables bound. One of this is yas-selected-text. You can therefore define a snippet like:

for ($1;$2;$3) {
yas-selected-text$0
}

to "wrap" the selected region inside your recently inserted snippet. Alternatively, you can also customize the variable yas-wrap-around-region to t which will do this automatically.

This snippets library aliases yas-selected-text to % here for convenience.

Hope that helps!

[hlissner]

Also: there are two unresolved comments in the last review. See above.

[benneti]

Ups, forgot to push this change and thanks for the reference.

[hlissner]

No problem! Thanks for the help!