message: Add a description of the or method in the manual
diff: @@ -82,6 +82,7 @@ The following are the currently-supported string methods:
  - [to_uppercase](#to_uppercase)
  - [escape](#escape)
  - [unescape](#unescape)
  +- [or](#or)
  ### ends_with
  @@ -451,6 +452,25 @@ echo $unescape($line)
  lamb
  ```
  +### or
  +
  +Defaults to string variables. Fallback to a given value if the variable is not defined
  +
  +#### Example
  +
  +```
  +echo $or($unknown_variable "Fallback")
  +let var = 42
  +echo $or($var "Not displayed")
  +```
  +
  +#### Output
  +
  +```
  +Fallback
  +42
  +```
  +
  ## Array Methods
  The following are the currently-supported array methods.
  @@ -612,3 +632,4 @@ echo @reverse([1 2 3])
  ```
  3 2 1
  ```
  +
  