feat(zig): add basic language statements. (#520)

Main source I used is from
[sublime-zig-language](https://github.com/ziglang/sublime-zig-language/tree/master/Snippets)
project. However I've customized some of the variants to be accessible
via the same shortcodes.

Author: sourcery-zone

snippets/zig-mode/elif

@@ -0,0 +1,7 @@
+# -*- mode: snippet -*-
+# name: else if statement
+# key: elif
+# --
+else if (${1}) {
+     ${0}
+}

snippets/zig-mode/else

@@ -0,0 +1,7 @@
+# -*- mode: snippet -*-
+# name: else sttement
+# key: el
+# --
+else {
+    $0
+}

snippets/zig-mode/enum

@@ -0,0 +1,7 @@
+# -*- mode: snippet -*-
+# name: enum declaration
+# key: enum
+# --
+enum${1:(${2:type})} {
+    $0
+}

snippets/zig-mode/fn

@@ -0,0 +1,7 @@
+# -*- mode: snippet -*-
+# name: fn name() type { ... }
+# key: fn
+# --
+fn ${1:name}($2) ${3:!void} {
+   $0
+}

snippets/zig-mode/for

@@ -0,0 +1,7 @@
+# -*- mode: snippet -*-
+# name: for statement
+# key: for
+# --
+for ($1) ${2:|${3:value}|} {
+    $0
+}

snippets/zig-mode/if

@@ -0,0 +1,7 @@
+# -*- mode: snippet -*-
+# name: if statement
+# key: if
+# --
+if ($1) {
+    $0
+}

snippets/zig-mode/imp

@@ -0,0 +1,5 @@
+# -*- mode: snippet -*-
+# name: import statement
+# key: imp
+# --
+const ${1:name} = @import("${2:lib}");

snippets/zig-mode/main

@@ -0,0 +1,7 @@
+# -*- mode: snippet -*-
+# name: main pub function
+# key: main
+# --
+pub fn main($1) ${2:${!void}} {
+    $0
+}

snippets/zig-mode/struct

@@ -0,0 +1,7 @@
+# -*- mode: snippet -*-
+# name: struct declaration
+# key: struct
+# --
+struct {
+    $0
+}

snippets/zig-mode/switch

@@ -0,0 +1,7 @@
+# -*- mode: snippet -*-
+# name: switch statement
+# key: switch
+# --
+switch ($1) {
+    $2 => $0
+}