Add support for parsing and generating JSON

This adds the std::json module, providing the means to parse JSON
strings and generate JSON strings from Inko objects. When parsing a JSON
string, the result is a std::json::Json value. These values in turn can
be converted (back) to JSON using Json.to_string and
Json.to_pretty_string.

The JSON parser is compliant with RFC 8259 and behaves as expected per
the tests from https://seriot.ch/projects/parsing_json.html. The parser
doesn't use a tokenizer as there's no need for one, and this reduces the
amount of allocations the parser needs.

This fixes https://gitlab.com/inko-lang/inko/-/issues/290.

Changelog: added

.gitattributes

@@ -0,0 +1 @@
+* text=auto eol=lf

libstd/src/std/float.inko

@@ -61,7 +61,7 @@ class builtin Float {
   #
   #     Float.parse('1.2e1') # => Option.Some(12.0)
   fn pub static parse(string: ref String) -> Option[Self] {
-    let res = _INKO.string_to_float(string)
+    let res = _INKO.string_to_float(string, -1, -1)
 
     if _INKO.is_undefined(res) { Option.None } else { Option.Some(res) }
   }

libstd/src/std/int.inko

@@ -42,7 +42,7 @@ class builtin Int {
   #     Int.from_base2('11') # => Option.Some(3)
   #     Int.from_base2('ff') # => Option.None
   fn pub static from_base2(string: ref String) -> Option[Self] {
-    let res = _INKO.string_to_int(string, 2)
+    let res = _INKO.string_to_int(string, 2, -1, -1)
 
     if _INKO.is_undefined(res) { Option.None } else { Option.Some(res) }
   }
@@ -57,7 +57,7 @@ class builtin Int {
   #     Int.from_base10('12') # => Option.Some(12)
   #     Int.from_base10('ff') # => Option.None
   fn pub static from_base10(string: ref String) -> Option[Self] {
-    let res = _INKO.string_to_int(string, 10)
+    let res = _INKO.string_to_int(string, 10, -1, -1)
 
     if _INKO.is_undefined(res) { Option.None } else { Option.Some(res) }
   }
@@ -76,7 +76,7 @@ class builtin Int {
   #     Int.from_base16('ef') # => Option.Some(239)
   #     Int.from_base16('zz') # => Option.None
   fn pub static from_base16(string: ref String) -> Option[Self] {
-    let res = _INKO.string_to_int(string, 16)
+    let res = _INKO.string_to_int(string, 16, -1, -1)
 
     if _INKO.is_undefined(res) { Option.None } else { Option.Some(res) }
   }