fix minor spelling errors and typos

Author: stmuk

lib/Type/Backtrace/Frame.pod

@@ -24,7 +24,7 @@ Returns the line number (line numbers start to count from 1).
 
     method code(Backtrace::Frame:D)
 
-Returns the code object into which C<.file> and C<.line> point, if avaialble.
+Returns the code object into which C<.file> and C<.line> point, if available.
 
 =head2 method subname
 

lib/Type/Capture.pod

@@ -4,7 +4,7 @@
 
     class Capture does Positonal does Associative { }
 
-A Capture is a an argument list for passing it to a code object.
+A Capture is an argument list for passing it to a code object.
 It contains a list-like part for positional arguments and a hash-like part
 for named arguments.
 

lib/Type/List.pod

@@ -381,7 +381,7 @@ Example:
     multi method combinations (List:D: Range:D $of = 0..*) returns List:D
     multi sub    combinations ($n, $k)                     returns List:D
 
-The C<Int> variant teturns all C<$of>-combinations of the invocant list.
+The C<Int> variant returns all C<$of>-combinations of the invocant list.
 For example
 
     say .join('|') for <a b c>.combinations(2);