docs: add examples for the article

examples/transaction-control/README.md

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+Examples in the folder are for the [article](https://ydb.tech/ru/docs/reference/ydb-sdk/recipes/tx-control) *Setting the transaction execution mode*
+
+To run examples
+
+Define *YDB_CONNECTION_STRING* and *YDB_TOKEN* environment variables
+
+Make new project by *npm i ydb-sdk* in clear folder
+
+And copy example code to this project
+
+```
+npx ts-node <example name>.ts
+```

examples/transaction-control/online-read-only.ts

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+import {Driver, TokenAuthService} from 'ydb-sdk';
+
+(async function () {
+    const driver = new Driver({
+        connectionString: process.env.YDB_CONNECTION_STRING,
+        authService: new TokenAuthService(process.env.YDB_TOKEN as string),
+    });
+    try {
+        await driver.tableClient.withSession(async (session) => {
+            const preparedQuery = await session.prepareQuery("SELECT 1");
+            await session.executeQuery(preparedQuery, {}, {beginTx: {onlineReadOnly: {allowInconsistentReads: false}}, commitTx: true});
+        });
+    } finally {
+        await driver.destroy();
+    }
+})();

examples/transaction-control/serializable.ts

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+import {Driver, TokenAuthService} from 'ydb-sdk';
+
+(async function () {
+    const driver = new Driver({
+        connectionString: process.env.YDB_CONNECTION_STRING,
+        authService: new TokenAuthService(process.env.YDB_TOKEN as string),
+    });
+    try {
+        await driver.tableClient.withSession(async (session) => {
+            const preparedQuery = await session.prepareQuery("SELECT 1");
+            const txMeta = await session.beginTransaction({serializableReadWrite: {}});
+            const txId = txMeta.id as string;
+            await session.executeQuery(preparedQuery, {}, {txId});
+            await session.commitTransaction({txId});
+        });
+    } finally {
+        await driver.destroy();
+    }
+})();

examples/transaction-control/snapshot-read-only.ts

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+import {Driver, TokenAuthService} from 'ydb-sdk';
+
+(async function () {
+    const driver = new Driver({
+        connectionString: process.env.YDB_CONNECTION_STRING,
+        authService: new TokenAuthService(process.env.YDB_TOKEN as string),
+    });
+    try {
+        await driver.tableClient.withSession(async (session) => {
+            const preparedQuery = await session.prepareQuery("SELECT 1");
+            const txMeta = await session.beginTransaction({snapshotReadOnly: {}});
+            const txId = txMeta.id as string;
+            await session.executeQuery(preparedQuery, {}, {txId});
+            await session.commitTransaction({txId});
+        });
+    } finally {
+        await driver.destroy();
+    }
+})();

examples/transaction-control/stale-read-only.ts

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+import {Driver, TokenAuthService} from 'ydb-sdk';
+
+(async function () {
+    const driver = new Driver({
+        connectionString: process.env.YDB_CONNECTION_STRING,
+        authService: new TokenAuthService(process.env.YDB_TOKEN as string),
+    });
+    try {
+        await driver.tableClient.withSession(async (session) => {
+            const preparedQuery = await session.prepareQuery("SELECT 1");
+            await session.executeQuery(preparedQuery, {}, {beginTx: {staleReadOnly: {}}, commitTx: true});
+        });
+    } finally {
+        await driver.destroy();
+    }
+})();