Add explicit "# key" directive to legacy snippet collection before deprecating filenames-as-triggers

snippets/ruby-mode/control structure/forin

@@ -1,4 +1,5 @@
 #name : for ... in ...; ... end
+# key: forin
 # --
 for ${1:element} in ${2:collection}
   $0

snippets/ruby-mode/control structure/if

@@ -1,4 +1,5 @@
 #name : if ... end
+# key: if
 # --
 if ${1:condition}
   $0

snippets/ruby-mode/control structure/ife

@@ -1,4 +1,5 @@
 #name : if ... else ... end
+# key: ife
 # --
 if ${1:condition}
   $2

snippets/ruby-mode/control structure/tim

@@ -1,3 +1,4 @@
 #name : times { |n| ... }
+# key: tim
 # --
 times { |${n}| $0 }

snippets/ruby-mode/control structure/until

@@ -1,4 +1,5 @@
 #name : until ... end
+# key: until
 # --
 until ${condition}
   $0

snippets/ruby-mode/control structure/upt

@@ -1,4 +1,5 @@
 #name : upto(...) { |n| ... }
+# key: upt
 # --
 upto(${n}) { |${i}|
   $0

snippets/ruby-mode/control structure/when

@@ -1,4 +1,5 @@
 #name : when ... end
+# key: when
 # --
 when ${condition}
   $0

snippets/ruby-mode/control structure/while

@@ -1,4 +1,5 @@
 #name : while ... end
+# key: while
 # --
 while ${condition}
   $0