snippet: add erlang-mode snippets

[Benjamin-Philip]

This commit adds initial support for Erlang snippets. These snippets
have been copied directly from the defaults.

• erlang-mode/after: Snippet for the after expression
• erlang-mode/begin: Snippet for the begin expression
• erlang-mode/beh: Snippet for the behaviour expression
• erlang-mode/case: Snippet for the case expression
• erlang-mode/compile: Snippet for the compile expression
• erlang-mode/def: Snippet for the define expression
• erlang-mode/exp: Snippet for the export expression
• erlang-mode/fun: Snippet for the fun expression
• erlang-mode/if: Snippet for the if expression
• erlang-mode/ifdef: Snippet for the ifdef expression
• erlang-mode/ifndef: Snippet for the ifndef expression
• erlang-mode/imp: Snippet for the import expression
• erlang-mode/inc: Snippet for the include expression
• erlang-mode/inc.lib: Snippet for the include_lib expression
• erlang-mode/loop: Snippet for the loop expression
• erlang-mode/rcv: Snippet for the recieve expression
• erlang-mode/rcv.after: Snippet for the receive after expression
• erlang-mode/rec: Snippet for the record expression
• erlang-mode/try: Snippet for the try expression
• erlang-mode/undef: Snippet for the undef expression

Close: #55
Ref: https://github.com/AndreaCrotti/yasnippet-snippets/tree/master/snippets/erlang-mode
Signed-off-by: Benjamin Philip [email protected]

---

• I searched the issue tracker and this hasn't been PRed before.
• My changes are not on the do-not-PR list for this project.
• My commits conform to the git conventions.
• My changes are visual; I've included before and after screenshots.
• I am blindly checking these off.
• Any relevant issues or PRs have been linked to.
• This a draft PR; I need more time to finish it.

[hlissner]

LGTM! Thanks for your help!

[Benjamin-Philip]

No problem!