feat add missing semi-colons in 'interest-is-interesting' (#739)

---- 
Co-authored-by: vaeng <[email protected]>

Author: Shankar Lohar

concepts/loops/about.md

@@ -57,7 +57,7 @@ int c{a++};
 The init component usually sets up a counter variable, the condition checks whether the loop should be continued or stopped and the post component usually increments the counter at the end of each repetition.
 
 ```cpp
-int sum{0}
+int sum{0};
 for (int i{1}; i < 10; ++i) {
   sum += i;
 }
@@ -91,4 +91,4 @@ for (int i{1}; i < 7; ++i) {
 }
 // equal_sum is now 12
 ```
-> Note: it is usually easier to understand the logic of the loop, when the use of `break` and `continue` is minimized or entirely avoided.
+> Note: it is usually easier to understand the logic of the loop, when the use of `break` and `continue` is minimized or entirely avoided.

concepts/loops/introduction.md

@@ -57,7 +57,7 @@ int c{a++};
 The init component usually sets up a counter variable, the condition checks whether the loop should be continued or stopped and the post component usually increments the counter at the end of each repetition.
 
 ```cpp
-int sum{0}
+int sum{0};
 for (int i{1}; i < 10; ++i) {
   sum += i;
 }
@@ -91,4 +91,4 @@ for (int i{1}; i < 7; ++i) {
 }
 // equal_sum is now 12
 ```
-> Note: it is usually easier to understand the logic of the loop, when the use of `break` and `continue` is minimized or entirely avoided.
+> Note: it is usually easier to understand the logic of the loop, when the use of `break` and `continue` is minimized or entirely avoided.

exercises/concept/interest-is-interesting/.docs/introduction.md

@@ -57,7 +57,7 @@ int c{a++};
 The _init component_ usually sets up a counter variable, the _condition_ checks whether the loop should be continued or stopped and the _post component_ usually increments the counter at the end of each repetition.
 
 ```cpp
-int sum{0}
+int sum{0};
 for (int i{1}; i < 10; ++i) {
   sum += i;
 }