Fix typo and grammar (#1329)

CppCoreGuidelines.md

@@ -5575,7 +5575,7 @@ An initialization explicitly states that initialization, rather than assignment,
     class A {   // Good
         string s1;
     public:
-        A(czstring p) : s1{p} { }    // GOOD: directly construct (and the C-sting is explicitly named)
+        A(czstring p) : s1{p} { }    // GOOD: directly construct (and the C-string is explicitly named)
         // ...
     };
 
@@ -6819,7 +6819,7 @@ Do *not* represent non-hierarchical domain concepts as class hierarchies.
 
 Here most overriding classes cannot implement most of the functions required in the interface well.
 Thus the base class becomes an implementation burden.
-Furthermore, the user of `Container` cannot rely on the member functions actually performing a meaningful operations reasonably efficiently;
+Furthermore, the user of `Container` cannot rely on the member functions actually performing meaningful operations reasonably efficiently;
 it may throw an exception instead.
 Thus users have to resort to run-time checking and/or
 not using this (over)general interface in favor of a particular interface found by a run-time type inquiry (e.g., a `dynamic_cast`).