Update linter to include eslint

Ref #1766

runtime/plugins/linter/help/linter.md

@@ -9,8 +9,10 @@ following filetypes and linters:
 * c++: g++
 * d: dmd
 * go: go build
+* haskell: hlint
 * java: javac
 * javascript: jshint
+* javascript: eslint
 * literate: lit
 * lua: luacheck
 * nim: nim
@@ -19,7 +21,7 @@ following filetypes and linters:
 * python: mypy
 * python: pylint
 * shell: shfmt
-* swift: swiftc
+* swift: swiftc (MacOS and Linux only)
 * yaml: yamllint
 
 If the linter plugin is enabled and the file corresponds to one of

runtime/plugins/linter/linter.lua

@@ -68,6 +68,7 @@ function init()
     makeLinter("gcc", "c", "gcc", {"-fsyntax-only", "-Wall", "-Wextra", "%f"}, "%f:%l:%c:.+: %m")
     makeLinter("g++", "c++", "gcc", {"-fsyntax-only","-std=c++14", "-Wall", "-Wextra", "%f"}, "%f:%l:%c:.+: %m")
     makeLinter("dmd", "d", "dmd", {"-color=off", "-o-", "-w", "-wi", "-c", "%f"}, "%f%(%l%):.+: %m")
+    makeLinter("eslint", "javascript", "eslint", {"-f","compact","%f"}, "%f: line %l, col %c, %m")
     makeLinter("gobuild", "go", "go", {"build", "-o", devnull, "%d"}, "%f:%l:%c:? %m")
     -- makeLinter("golint", "go", "golint", {"%f"}, "%f:%l:%c: %m")
     makeLinter("hlint", "haskell", "hlint", {"%f"}, "%f:%l:%c.-: %m")