Optional line endings for `GrammarError.format`

Also in peg$SyntaxError.prototype.format in generate-js.js. We always use "\n" for line endings. Although this probably works in modern Windows, for most cases, it’s probably better to have a default second parameter for lineEnding. From the CLI, we can pass in node’s os.EOL. We can’t use os in the generated code, since it needs to run in the browser.

[hildjj]

peg.js supported many old browsers, and there are a good number of people using it there, from what I can tell. Some of them should probably be pre-compiling their grammars, and we should probably change the docs to make that more clear. Since peg.js supported it, and we care about backward-compatibility, we need to support it too. If nothing else, the online playground is a useful tool for people to learn about Peggy.

I’m open to dropping support for IE 11, which I’ll probably argue for in 3.0, which will mean we will be able to modernize the browser-bound JS quite a bit.

Note that we do use node libraries in the CLI, where we know that the environment is going to be node.

[tornikeshavishvili]

I thought regarding new line and does not seem to be very important at this point, because existing implementation has proved itself as is.