Revisit whether to remove specific var backward compatibility for #150

[kensoh]

Prior to #150 the use of var to declare a local variable, followed by some type of non-web-element steps (such as echo, api, if), will let the steps be able to access the locally defined variable. For such niche cases, it is working not by design.

After #150, the locally defined variable will not be accessible by those non-web-element steps. This issue is to evaluate whether to enable backward compatibility by auto-making var declarations to be broader in scope. More details here - #150 (comment) and #150 (comment)

[kensoh]

Previous notes -

For backward compatibility, it is easy to update TagUI translation engine to always convert var variable_name = xxx to variable_name = xxx but this prevents advanced users who wants to limit scope of a variable within a section of JavaScript code from implementing good programming practices. Thus keep it flexible so that users can write variable_name = xxx according to TagUI documentation, or use var variable_name = xxx if they wish to limit scope for just that few consecutive JS statements.

[kensoh]

After weighing and discussing best practices with @Aussiroth and @lohvht, decision is not to auto-remove the use of var. Nothing needs to be done for readme or samples as they already use = directly for declaration.

May consider creating a helper script to auto-process old scripts into new ones for convenience of users. Though not recommended as users should decide rather than being auto-upgraded and may be interpreted incorrectly.