Parse unhandled CSI and OSC sequences correctly

For example, for "\e\e[31mHello", continue parsing instead of exiting
escape mode at the second \e

fish sends modifyOtherKeys even in TERM=linux, dirtying the prompt

It fixes the fish default prompt, which sends unsupported escape codes
even with TERM=linux

Reviewed-on: https://codeberg.org/mintsuki/flanterm/pulls/23

[WIP] Optimize put_char, split out specific unscaled code path

Add a gitignore

Also limit the resolution of the terminal if necessary and force no-canvas mode if using bump allocator

* Terminal optimization option added : flanterm_toggle_masking()

* Terminal optimization option added

* error correction

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Co-authored-by: ernestbedight <bob@bedight.localdomain>

Fix include guard

Fix -Wsign-conversion warnings

Fix compiler warning regarding inlining

backends/fb: Basic support for different framebuffer configurations