charcode

Update and adapt to lints.

• Updates generator to write into existing file without clobbering it.
• Changes the -h flag to be -H, so -h works for help. (Technically breaking, if anyone uses the flag.)
• Adds verbose flag.

• Optimize for Pub score.

• Add camelCase constant names as alternatives for current snake_case constants. Example $doubleQuote as alternative to $double_quote.
• Internal tweaks to flag parsing.
• Switch to using package:lints.

• Stable release for null safety.

• Update SDK constraints to >=2.12.0-0 <3.0.0 based on beta release guidelines.

• Allow prerelease versions of the 2.12 sdk.

• Add command line functionality to generate constants. Allows clients to generate their own constants instead of depending on the package at run-time. Example: To generate the characters needed for a hexadecimal numeral, run pub run charcode a-fA-F\d+-.

• Allow 2.10 stable and 2.11.0 dev SDK versions.

• Opt in to null safety.

• Added example, changed lints.

• Updated the SDK constraint.

• Spelling and linting fixes.

Update README.md

Build badge.

• Initial version