Update tutorial files

Author: xuniq

doc/code_snippets/snippets/mysql/README.md

@@ -0,0 +1,11 @@
+# Improving MySQL with Tarantool
+
+A sample application that is used in [Improving MySQL with Tarantool](https://www.tarantool.io/en/doc/latest/how-to/sql/improving_mysql/) tutorial.
+
+## Running
+
+To run applications placed in [instances.enabled](instances.enabled), go to the `mysql` directory in the terminal and execute the `tt start` command, for example:
+
+```console
+$ tt start example
+```

doc/code_snippets/snippets/mysql/instances.enabled/config.yaml

@@ -0,0 +1,25 @@
+app:
+  file: 'example.lua'
+
+groups:
+  group001:
+    replicasets:
+      replicaset001:
+        instances:
+          instance001:
+            iproto:
+              listen: "3301"
+            memtx:
+              memory: 128 * 1024 * 1024
+              min_tuple_size: 16
+              max_tuple_size: 128 * 1024 * 1024
+            wal:
+              mode: "none"
+              wal_max_size: 56 * 1024 * 1024
+            snapshot:
+              by_interval: 60 * 60
+              count: 6
+            log:
+              level: 7
+            fiber:
+              too_long_threshold: 0.5

doc/code_snippets/snippets/mysql/instances.enabled/example.lua

@@ -0,0 +1,17 @@
+-- example.lua --
+
+box.schema.user.grant('guest','read,write,execute','universe')
+
+local function bootstrap()
+    if not box.space.mysqldaemon then
+        s = box.schema.space.create('mysqldaemon')
+        s:create_index('primary',
+        {type = 'tree', parts = {1, 'unsigned'}, if_not_exists = true})
+    end
+    if not box.space.mysqldata then
+        t = box.schema.space.create('mysqldata')
+        t:create_index('primary',
+        {type = 'tree', parts = {1, 'unsigned'}, if_not_exists = true})
+    end
+end
+bootstrap()

doc/code_snippets/snippets/mysql/instances.enabled/instances.yml

@@ -0,0 +1 @@
+instance001:

doc/contributing/docs/markup/code.rst

@@ -56,9 +56,9 @@ For code snippets, we use the ``code-block:: language``
 You can enable syntax highlighting if you specify the language for the snippet.
 The most commonly used highlighting languages are:
 
-*   ``tarantoolsession``—interactive Tarantool session,
+*   ``tarantoolsession`` -- interactive Tarantool session,
     where command lines start with ``tarantool>`` prompt.
-*   ``console``—interactive console session, where command lines
+*   ``console`` -- interactive console session, where command lines
     start with ``$`` or ``#``.
 *   ``lua``, ``bash`` or ``c`` for programming languages.
 *   ``text`` for cases when we want the code block to have no highlighting.