Enhance regex to recognize variables

[igorlima]

It looks like when assigning another variable to another it's not being recognised by ctags. Also when any string is set by back-tick, or set by string template, it's not being recognised too.

Given the js file below

const year = 1984
const month = `october`
const day = '21'
const birthday = year + 'y' + month + 'm' + day + 'd'

we can use the command bellow to test it out:

ctags  -f - --format=2 --excmd=pattern --fields=nks <filename>

BEFORE

As it is today, we have the following output from ctags

day	test-test.js	/^const day = '21'$/;"	V	line:3
year	test-test.js	/^const year = 1984$/;"	V	line:1

AFTER

After applying this enhancement, we start getting the following output

birthday	test-test.js	/^const birthday = year + 'y' + month + 'm' + day + 'd'$/;"	V	line:4
day	test-test.js	/^const day = '21'$/;"	V	line:3
month	test-test.js	/^const month = `october`$/;"	V	line:2
year	test-test.js	/^const year = 1984$/;"	V	line:1