Cleanup documentation (#4667)

* Cleanup documentation

* Fix comment typo in fmt::formatter struct

* Fix formatting and grammar in api.md

Corrected formatting and grammar in the API documentation.

Author: ssszcmawo

doc/api.md

@@ -28,7 +28,7 @@ dependencies for better compile times. This header is only beneficial when
 using {fmt} as a library (the default) and not in the header-only mode.
 It also provides `formatter` specializations for the following types:
 
-- `int`, `long long`,
+- `int`, `long long`
 - `unsigned`, `unsigned long long`
 - `float`, `double`, `long double`
 - `bool`
@@ -105,8 +105,8 @@ Example ([run](https://godbolt.org/z/nvME4arz8)):
       fmt::print("{}\n", kevin_namespacy::film::se7en); // Output: 7
     }
 
-Using specialization is more complex but gives you full control over
-parsing and formatting. To use this method specialize the `formatter`
+Using a specialization is more complex, but gives you full control over
+parsing and formatting. To use this method, specialize the `formatter`
 struct template for your type and implement `parse` and `format`
 methods.
 
@@ -515,7 +515,7 @@ chrono-format-specifications).
 
 ### Variants
 
-A `std::variant` is only formattable if every variant alternative is
+A `std::variant` can be formatted only if every alternative is
 formattable, and requires the `__cpp_lib_variant` [library
 feature](https://en.cppreference.com/w/cpp/feature_test).
 
@@ -719,7 +719,7 @@ configuring CMake.
 ### CMake Options
 
 - **`FMT_OS`**: When set to `OFF`, disables OS-specific APIs (`fmt/os.h`).
-- **`FMT_UNICODE`**: When set of `OFF`, disables Unicode support on
+- **`FMT_UNICODE`**: When set to `OFF`, disables Unicode support on
   Windows/MSVC. Unicode support is always enabled on other platforms.
 
 ### Macros

include/fmt/printf.h

@@ -473,7 +473,7 @@ void vprintf(buffer<Char>& buf, basic_string_view<Char> format,
     }
 
     auto arg = get_arg(arg_index);
-    // For d, i, o, u, x, and X conversion specifiers, if a precision is
+    // For d, i, o, u, x and X conversion specifiers, if a precision is
     // specified, the '0' flag is ignored
     if (specs.precision >= 0 && is_integral_type(arg.type())) {
       // Ignore '0' for non-numeric types or if '-' present.
@@ -586,7 +586,7 @@ inline auto vsprintf(basic_string_view<Char> fmt,
 
 /**
  * Formats `args` according to specifications in `fmt` and returns the result
- * as as string.
+ * as string.
  *
  * **Example**:
  *