emit useless space and fix indentations

SC2034.md

@@ -1,39 +1,41 @@
 # foo appears unused. Verify it or export it.
 
-### Problematic code:
+## Problematic code:
 
 ```sh
 foo=42
 echo "$FOO"
 ```
 
-### Correct code:
+## Correct code:
 
 ```sh
 foo=42
 echo "$foo"
 ```
 
-### Rationale:
+## Rationale:
 
 Variables not used for anything are often associated with bugs, so ShellCheck warns about them.
 
 Also note that something like `local let foo=42` does not make a `let` statement local -- it instead declares an additional local variable named `let`.
 
-### Exceptions
+## Exceptions
 
 This warning may be falsely emitted when a variable is only referenced indirectly, and for variables that are intentionally unused.
 
-#### Indirection
+### Indirection
 
 It's ShellCheck's intended behavior to emit this warning for any variable that is only referenced though indirection:
 
+```sh
 # foo generates a warning, even though it has five indirect references
 foo=42
 name=foo
 echo "${!name} $((name))"
 export "$name"; eval "echo $name"
 declare -n name; echo "$name"
+```
 
 This is an intentional design decision and not a bug. If you have variables that will not have direct references, consider using an associative array in bash, or just [[Ignore]] the warning. 
 
@@ -55,7 +57,7 @@ echo "$last, $zip"
 
 Or optionally as a prefix for dummy variables (ShellCheck >0.7.2).
 
-``` ​
+```sh ​
 read _first last _email zip _lat _lng <<< "$str"
 echo "$last, $zip"
 ```
@@ -66,4 +68,4 @@ For versions <= 0.7.2, the message can optionally be [[ignore]]d with a directiv
 # shellcheck disable=SC2034  # Unused variables left for readability
 read first last email zip lat lng <<< "$str"
 echo "$last, $zip"
-``
+```