Replace more quotes with admonition blocks in docs

lib/elixir/lib/application.ex

@@ -636,10 +636,14 @@ defmodule Application do
   If the configuration parameter does not exist, the function returns the
   `default` value.
 
-  > **Important:** you must use this function to read only your own application
+  > #### Warning {: .warning}
+  >
+  > You must use this function to read only your own application
   > environment. Do not read the environment of other applications.
 
-  > **Important:** if you are writing a library to be used by other developers,
+  > #### Application environment in libraries {: .info}
+  >
+  > If you are writing a library to be used by other developers,
   > it is generally recommended to avoid the application environment, as the
   > application environment is effectively a global storage. For more information,
   > read our [library guidelines](library-guidelines.md).
@@ -693,10 +697,14 @@ defmodule Application do
 
   If the configuration parameter does not exist, the function returns `:error`.
 
-  > **Important:** you must use this function to read only your own application
+  > #### Warning {: .warning}
+  >
+  > You must use this function to read only your own application
   > environment. Do not read the environment of other applications.
 
-  > **Important:** if you are writing a library to be used by other developers,
+  > #### Application environment in info
+  >
+  > If you are writing a library to be used by other developers,
   > it is generally recommended to avoid the application environment, as the
   > application environment is effectively a global storage. For more information,
   > read our [library guidelines](library-guidelines.md).
@@ -716,10 +724,14 @@ defmodule Application do
 
   If the configuration parameter does not exist, raises `ArgumentError`.
 
-  > **Important:** you must use this function to read only your own application
+  > #### Warning {: .warning}
+  >
+  > You must use this function to read only your own application
   > environment. Do not read the environment of other applications.
 
-  > **Important:** if you are writing a library to be used by other developers,
+  > #### Application environment in info
+  >
+  > If you are writing a library to be used by other developers,
   > it is generally recommended to avoid the application environment, as the
   > application environment is effectively a global storage. For more information,
   > read our [library guidelines](library-guidelines.md).

lib/elixir/lib/config.ex

@@ -34,7 +34,9 @@ defmodule Config do
   `Config` also provides a low-level API for evaluating and reading
   configuration, under the `Config.Reader` module.
 
-  > **Important:** if you are writing a library to be used by other developers,
+  > #### Avoid application environment in libraries {: .info}
+  >
+  > If you are writing a library to be used by other developers,
   > it is generally recommended to avoid the application environment, as the
   > application environment is effectively a global storage. Also note that
   > the `config/config.exs` of a library is not evaluated when the library is

lib/elixir/lib/kernel.ex

@@ -3454,8 +3454,10 @@ defmodule Kernel do
   will be available at compile-time. Custom attributes may be configured to
   behave closer to Erlang by using `Module.register_attribute/3`.
 
-  > **Important:** Libraries and frameworks should consider prefixing any
-  > module attributes that are private by underscore, such as `@_my_data`
+  > #### Prefixing module attributes {: .tip}
+  >
+  > Libraries and frameworks should consider prefixing any
+  > module attributes that are private by underscore, such as `@_my_data`,
   > so code completion tools do not show them on suggestions and prompts.
 
   Finally, note that attributes can also be read inside functions:

lib/elixir/lib/kernel/special_forms.ex

@@ -1223,7 +1223,9 @@ defmodule Kernel.SpecialForms do
   reported to where `defadd` was invoked. `location: :keep` affects
   only definitions inside the quote.
 
-  > **Important:** do not use `location: :keep` if the function definition
+  > #### `location: :keep` and unquote {: .warning}
+  >
+  > Do not use `location: :keep` if the function definition
   > also `unquote`s some of the macro arguments. If you do so, Elixir
   > will store the file definition of the current location but the
   > unquoted arguments may contain line information of the macro caller,

lib/elixir/lib/system.ex

@@ -489,8 +489,10 @@ defmodule System do
   @doc """
   Traps the given `signal` to execute the `fun`.
 
-  > **Important**: Trapping signals may have strong implications
-  > on how a system shuts down and behave in production and
+  > #### Avoid setting traps in libraries {: .warning}
+  >
+  > Trapping signals may have strong implications
+  > on how a system shuts down and behaves in production and
   > therefore it is extremely discouraged for libraries to
   > set their own traps. Instead, they should redirect users
   > to configure them themselves. The only cases where it is
@@ -911,7 +913,9 @@ defmodule System do
 
   It uses `sh` for Unix-like systems and `cmd` for Windows.
 
-  > **Important:**: Use this function with care. In particular, **never
+  > #### Watch out {: .warning}
+  >
+  > Use this function with care. In particular, **never
   > pass untrusted user input to this function**, as the user would be
   > able to perform "command injection attacks" by executing any code
   > directly on the machine. Generally speaking, prefer to use `cmd/3`