symbols: Enable writing keysyms list as UTF-8 strings Each Unicode code point of the string will be translated to their respective keysym, if possible. An empty string denotes `NoSymbol`. When such conversion is not possible, this will raise a syntax error. This introduces the following syntax: ```c // Empty string = `NoSymbol` key <1> {[""]}; // NoSymbol // Single code point = single keysym key <2> {["é"]}; // eacute // String = translate each code point to their respective keysym key <3> {["sßξك🎺"]}; // {s, ssharp, Greek_xi, Arabic_kaf, U1F3BA} // Mix string and keysyms key <4> {[{"ξ", Greek_kappa, "β"}]}; // { Greek_xi, Greek_kappa, Greek_beta} ``` It can also be used wherever a keysym is required, e.g. in `interpret` and `modifier_map` statements. In these cases a single keysym is expected, so the string should contain *exactly one* Unicode code point.