(FunC) Add clarifications for literals and identifiers (#1177)

* Update literals_identifiers.md

* Update literals_identifiers.md

* proofread

---------

Co-authored-by: AlexG <39581753+reveloper@users.noreply.github.com>

Author: memearchivarius

docs/v3/documentation/smart-contracts/func/docs/literals_identifiers.md

@@ -10,16 +10,25 @@ Examples of valid literals: `0`, `123`, `-17`, `00987`, `0xef`, `0xEF`, `0x0`, `
 ## String literals
 
 In FunC, strings are enclosed in double quotes `"`, like `"this is a string"`.<br />
-Special characters like `\n` and multi-line strings are not supported.<br />
-Optionally, a type can be specified after a string literal, such as `"string"u`.
+You can optionally specify a type after the string literal, such as `"string"u`.<br />
+Special characters like `\n` are not supported, but you can create multi-line <br />  strings simply by writing the text across multiple lines, like this:
+```
+;; somewhere inside of a function body
+
+var a = """
+   hash me baby one more time
+"""h;
+var b = a + 42;
 
+b; ;; 623173419
+```
 
 FunC supports the following string types:
 * without type – Used for `asm` function definitions and defining a slice constant from an ASCII string.
 * `s`— Defines a raw slice constant using its contents (hex-encoded and optionally bit-padded).
 * `a`— Creates a slice constant containing a `MsgAddressInt` structure from a given address.
 * `u`— Converts an ASCII string into an integer constant, representing its hex values.
-* `h`— Generates an integer constant from the first 32 bits of the string’s SHA-256 hash.
+* `h`— Generates an integer constant from the first 32 bits of the string's SHA-256 hash.
 * `H`— Generates an integer constant from the full 256-bit SHA-256 hash of the string.
 * `c`— Generates an integer constant from the `crc32` value of the string.
 
@@ -38,13 +47,14 @@ The following string literals produce these corresponding constants:
 
 FunC allows a broad range of identifiers for functions and variable names. 
 Any **single-line string** that meets the following conditions qualifies as a valid identifier:
-- It **does not** contain special symbols: `;`, `,`, `(`, `)`, ` ` spaces including tabs, `~`, and `.`.
+- It **does not** contain special symbols: `;`, `,`, `(`, `)`, `[`, `]`, spaces including tabs, `~`, and `.`.
 - It **does not** start as a comment or a string literal (i.e., with `"` at the beginning). 
 - It is **not** a number literal.
 - It is **not** an underscore `_`.
 - It is **not** a reserved keyword. Exception: if it starts with a backtick `` ` ``, it must also end with a backtick and cannot contain any additional backticks inside.
+- It is **not** a name of a [builtin](https://github.com/ton-blockchain/ton/blob/5c392e0f2d946877bb79a09ed35068f7b0bd333a/crypto/func/builtins.cpp#L1133).
 
-Additionally, function names in function definitions can start with `.` or `~`.
+Additionally, **function** names in function definitions can start with `.` or `~`.
 
 Examples of valid identifiers:
 - `query`, `query'`, `query''`
@@ -130,4 +140,3 @@ all optimizations and pre-computations apply efficiently—unlike the older appr
 
 
 <Feedback />
-