fix(doc): improve compiler section wording and TON Blockchain intro (#3465)

Author: sergfgg1212

docs/src/content/docs/book/index.mdx

@@ -17,7 +17,7 @@ Here are its main contents:
 
 1. #### Quick start
 
-   The Book begins with a few scenic tours and cheat sheets to get you started immediately. First, it briefly discusses TON Blockchain and how smart contracts work there, then gives an overview of many syntax and semantical aspects of the Tact language.
+   The Book begins with a few scenic tours and cheat sheets to get you started immediately. First, it briefly introduces the TON Blockchain and how Tact smart contracts work there, then it gives an overview of many syntax and semantical aspects of the Tact language.
 
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@@ -67,7 +67,7 @@ Here are its main contents:
 
    The subsection [Going places](/book/compile) explains how to compile, debug, and test Tact contracts locally. From there, it moves on to provide descriptions of deploying contracts to the TON Blockchain.
 
-   Lastly, it shows how to further tweak the compiler with its configuration options, interface with existing FunC code, and discusses best practices for securing your smart contracts.
+   Lastly, it shows how to further tweak the compiler with its configuration options, interface with existing FunC code, and apply best practices to secure your smart contracts.
 
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