feat: add syntax sample for dotEnv files

tests/syntax-tests/source/DotENV/.env

@@ -0,0 +1,57 @@
+# Keyword
+export TEST_KEYWORD="bar"
+export TEST_KEYWORD=12345
+export TEST_KEYWORD=TRUE
+
+# Variable
+TEST_VARIABLE="Hello"
+
+# String interpolation
+TEST_INTERPOLATION_VARIABLE="$VAR1 test test$VAR2test test"
+TEST_INTERPOLATION_SYNTAX_ONE="test test{$NVAR1}test{$NVAR2}test test"
+TEST_INTERPOLATION_SYNTAX_TWO="test test${NVAR1}test${NVAR2}test test"
+TEST_INTERPOLATION_SYNTAX_ALL="test$VAR1test test {VAR2}test test${VAR3}test"
+
+# Unquoted
+TEST_UNQUOTED=bar
+TEST_UNQUOTED_NO_VALUE=
+
+# White spaced
+TEST_WHITE_SPACE =
+TEST_WHITE_SPACE_STRING = "Hello"
+TEST_WHITE_SPACE_UNQUOTED = bar
+TEST_WHITE_SPACE_UNQUOTED_BOOL = false
+TEST_WHITE_SPACE_UNQUOTED_NUM = 20
+
+# language constants
+TEST_TRUE=true
+TEST_FALSE=false
+TEST_NULL=null
+TEST_TRUE_CAPITAL=TRUE
+TEST_FALSE_CAPITAL=FALSE
+TEST_NULL_CAPITAL=NULL
+
+# Numerical values
+TEST_NUM_DECIMAL=54
+TEST_NUM_FLOAT=5.3
+TEST_NUM=1e10
+TEST_NUM_NEGATIVE=-42
+TEST_NUM_OCTAL=057
+TEST_NUM_HEX=0x1A
+
+# Comments
+#TEST_ONE=foobar
+# TEST_TWO='foobar'
+# TEST_THREE="foobar" # a comment on a commented row
+TEST_FOUR="test test test" # this is a comment
+TEST_FIVE="comment symbol # inside string" # this is a comment
+TEST_SIX="comment symbol # and quotes \" \' inside quotes" # " this is a comment
+
+# Escape sequences
+TEST_ESCAPE="escaped characters \n \t \r \" \' \$ or maybe a backslash \\..."
+
+# Double Quotes
+TEST_DOUBLE="Lorem {$VAR1} ${VAR2} $VAR3 ipsum dolor sit amet\n\r\t\\"
+
+# Single Quotes
+TEST_SINGLE='Lorem {$VAR1} ${VAR2} $VAR3 ipsum dolor sit amet\n\r\t\\'