docs: add @Alert unsafe

Author: illusory0x0

builtin/option.mbt

@@ -31,7 +31,7 @@ pub fn Option::to_string[X : Show](self : X?) -> String {
 
 ///|
 /// Extract the value in `Some`.
-/// Panic if input is `None`.
+/// @alert unsafe "Panic if input is `None`."
 pub fn Option::unwrap[X](self : X?) -> X {
   match self {
     None => panic()

builtin/string.mbt

@@ -70,7 +70,7 @@ fn code_point_of_surrogate_pair(leading : Int, trailing : Int) -> Char {
 ///
 /// # Panics
 ///
-/// Panics if the index is out of bounds.
+/// @alert unsafe "Panics if the index is out of bounds."
 pub fn charcode_at(self : String, index : Int) -> Int {
   guard index >= 0 && index < self.length() else {
     abort("index out of bounds")

immut/priority_queue/priority_queue.mbt

@@ -127,7 +127,7 @@ pub fn pop[A : Compare](self : T[A]) -> T[A]? {
 ///|
 /// Pops the first value from the immutable priority queue.
 ///
-/// Panics if the queue is empty.
+/// @alert unsafe "Panics if the queue is empty."
 /// # Example
 /// ```
 /// let queue = @priority_queue.of([1, 2, 3, 4])

string/string.mbt

@@ -692,7 +692,7 @@ pub fn pad_end(self : String, total_width : Int, padding_char : Char) -> String
 ///
 /// # Panics
 ///
-/// Panics if the index is out of bounds.
+/// @alert unsafe "Panics if the index is out of bounds."
 pub fn String::rev_get(self : String, index : Int) -> Char {
   guard index >= 0 else { abort("index out of bounds") }
   for utf16_offset = self.charcode_length() - 1, char_count = 0