Prepend identifiers with _ when they begin with digit.

[daniel-yeow]

Using ./bin/dict_generator -output example/diam/const.js -dictionary dict/extra.xml generates a dictionary that contains

 // Rx
    5GSRANNASReleaseCause:                        572,
    5GMMCause:                                    573,
    5GSMCause:                                    574,

which eventually results with syntax

SyntaxError: file:///mnt/example/diam/const.js: Identifier directly after number (637:5)
  635 |     ExtendedAPNAMBRUL:                            2849,
  636 |     // Rx
> 637 |     5GSRANNASReleaseCause:                        572,
      |      ^
  638 |     5GMMCause:                                    573,
  639 |     5GSMCause:                                    574,
  640 |     NGAPCause:                                    575,
        at <internal/k6/compiler/lib/babel.min.js>:7:10099(24)

Prepending with _ will solve that problem for any digit.

[lwlee2608]

Thanks!